Method of using a chemical indicator

ABSTRACT

A sterilization indicator having sterilizing agent sensitive indicia is described. The indicator allows a sterilization cycle to be monitored without the need for a user to subjectively distinguish between color, quality or intensity of display patterns.

FIELD

This invention relates to sterilization indicators, sterilizationinformation and methods of monitoring articles to be sterilized. Thepresent invention relates particularly to a sterilization indicator thatcan be machine read to provide a user with information relating to asterilization process. With the present invention, information relatingto the efficacy of a sterilization cycle can be machine read and/orelectronically linked to integrated electronic information systemsthroughout the health care provider system.

BACKGROUND

Sterilization is the act of killing bacteria and other microorganisms onsurgical instruments, devices and implants. Sterilizers are designed tokill all viable living organisms within a sterilization chamber. This ischallenging, as objects can be contaminated with any of a number ofdifferent types of bacteria, some more dangerous and tougher to killthan others.

Sterilization indicators show whether a sterilizer achieved adequate(e.g. lethal) conditions. One kind of sterilization indicator is knownas a chemical indicator. Chemical indicators respond to one or more ofthe critical parameters of a sterilization process. Typically, chemicalindicators either change color or have a moving front with an endpointto provide information concerning the sterilization process.

The Association for the Advancement of Medical Instrumentation {AAMI}has recommended practices and standards that cover sterilizationtesting, including the use of chemical indicators. Hospitals frequentlylook to AAMI to establish sterilization assurance procedures. See e.g.Good Hospital Practice: Steam Sterilization and Sterility Assurance,AAMI Recommended Practice, Section 6.4 (1988). Hospitals also look toother standards and regulatory agencies for validation, routine controland other procedures for obtaining, recording, and interpreting data toshow that a sterilization process complies with a predeterminedsterility assurance level. Other recommendations and guidelines areprovided by the Joint Commission on Accreditation of Hospitals (JCAH),the Center for Disease Control, Association of Operating Room Nurses(AORN), American Society for Healthcare Central Services Personnel(ASHCSP), and the various state laws.

AAMI categorizes chemical indicators in five classes. See Sterilizationof Health Care Products—Chemical Indicators—Part 1: GeneralRequirements, American National Standards Institute (ANSI)/AAMI ST60-(1996). Class 1 relates to process indicators. Process indicators areintended for use with individual packs to demonstrate that the pack hasbeen exposed to the sterilization process and to distinguish betweenprocessed and unprocessed packs. Class 2 describes indicators for use ina specific test procedure such as a Bowie-Dick test. Class 3 relates tosingle parameter indicators, and class 4 to multi-parameter indicators.Multi-parameter indicators are designed to respond to two or morecritical parameters of sterilization and indicate exposure to asterilization cycle at stated values of the chosen parameters. Forexample, time, temperature and saturated steam are critical conditionsfor a steam cycle. Class 5 chemical indicators are known as integratingindicators. These are indicators designed to react to all criticalparameters over a specific range of sterilization cycles. Integratingchemical indicators are described in U.S. Pat. Reexamination CertificateNo. B1—3,981,683, (Larsson et al.) and U.S. Pat. Reissue No. 34,515 toFoley. Other chemical indicators are described in U.S. Pat. Nos.3,114,349; 3,313,266; 3,341,238; 3,652,249; 4,138,216; 4,382,063;4,576,795; 4,692,307; 4,579,715; and 5,451,372 (the entire contents ofeach of which are herein incorporated by reference).

Another kind of sterilization indicator is known as a biologicalindicator. Biological indicators use a large number (usually a millionor more) of microorganisms that are highly resistant to the sterilizingagent of the sterilization cycle being monitored. See Sterilization ofHealth Care Products—Biological Indicators—Part 1: General Requirements,ANSI/AAMI ST 59 (incorporated herein by reference). Biological indicatortechnology is also disclosed in U.S. Pat. Nos. 3,661,717 and 5,073,088(the entire contents of which are herein incorporated by reference).

Minnesota Mining and Manufacturing Company (3M) sells Attest™ RapidReadout Biological Monitoring Systems. These systems include abiological indicator that is capable of exhibiting fluorescence after afailed (non-lethal) sterilization cycle, and an auto reader. To test asteam sterilizer with an Attest system, the user places the biologicalsterilization indicator into the steam sterilizer along with the itemsto be sterilized. After the sterilization cycle, the indicator is placedin an Attest auto reader (e.g. model 190). The auto reader has anincubator and a means for reading the biological indicator to determinewhether the sterilization indicator exhibits fluorescence. If the steamsterilization cycle was lethal, the auto reader will not detectfluorescence within a predetermined time. If the cycle was non-lethal,the auto reader will detect fluorescence associated with the biologicalsterilization indicator in the predetermined time. Even with thisinstrumentation, a user is required to manually record the resultsprovided by the auto reader.

Other international standards organizations and regulatory agenciesdescribe sterilization indicators for monitoring sterilization processesin the health care context. The International Organization forStandardization (ISO) includes many standards similar to those describedabove. See ISO 11140-1:1995 for chemical indicators. European StandardNos. EN 867-1 and 866-1 also include many standards similar, but notidentical to those of AAMI and ISO (see e.g. The European Committee forStandardization's European Standard No. EN 867-1, Non-biological systemsfor use in sterilizers—Part 1: General requirements).

When a U.S. hospital designs its sterilization assurance practices, itoften evaluates equipment control, exposure control, pack control andload control. Equipment control evaluates sterilizer performance. Forexample, a Bowie-Dick pack can indicate the failure of the vacuumportion of a steam sterilization cycle. Load control is often abiological indicator placed in the sterilization chamber.

Items to be sterilized are often wrapped in sterilization wrap. The wrapis typically secured with an exposure control indicator (e.g. indicatortape). The resultant assembly is referred to as a pack. Exposure controlis typically a chemical indicator placed within the sterilizationchamber but outside the pack that is being sterilized. Exposure controlidentifies processed from unprocessed packs. Pack control is usually asterilization indicator placed within a pack that evaluates conditionsinside an individual pack. After a successful sterilization cycle, thearticles within the sterilization packs remain sterile until the pack isopened. As a result, packs are usually opened in a specially preparedand maintained sterile field in the operating room just prior to theiruse. However, commercially available sterilization indicators foundwithin packs cannot be read prior to opening the pack becausesterilization wrap is typically opaque. If the sterilization indicatorinside a pack indicates a failed sterilization cycle, there are manyproblems in finding out about it just prior to use of the items withinthe pack. The problems are multiplied when the sterilization indicatoridentifying a failure is found within the specially prepared andmaintained sterile field.

The importance of sterilization assurance in hospitals requires constantattempts to better utilize sterilization indicators. A user typicallyvisually inspects chemical indicators to obtain information from theindicator. Some users find it difficult to subjectively determinewhether a chemical indicator has changed color. This is particularly aproblem for a user who suffers from color blindness. For example, somepersons who suffer from color blindness have difficulty distinguishingred colors from green colors. The Propper Gas-ChexOR and Steri-DotIndicators (Model No. 361001) change from a red color to green uponexposure to ethylene oxide gas. This color change may be difficult forsome users to distinguish with the attendant risk of inaccuraterecordation of sterilization information. Another indicator with a colorchange that is difficult to perceive is the Surgicot® Version 3.0Universal Integrator. This integrator includes a steam color change barfrom yellow to brown. The contrast between these particular colors isdifficult for some users to perceive.

Biological indicators suffer from some of the same problems as chemicalindicators. U.S. Pat. Nos. 5,030,832; 5,063,297; 5,334,841 and 5,863,790(the entire contents of each of which are herein incorporated byreference) describe electronic reading apparatus for objectively readingfluorescence of biological indicators.

Accuracy of information relating to the state of objects in thesterilization process at a healthcare facility (e.g. a hospital) is veryimportant. Access to this information is also important. There are manyways that human error can adversely affect a hospital's sterilizationassurance procedures. Operators can err in capturing data (e.g.transpose numbers, improperly key-in information to a computer),perceiving information (e.g. the color blindness issue discussed above)and recording data, to name just a few. Because sterilization indicatorsare small, they can simply become lost, especially if their use entailstransportation between different hospital functions, locations ordepartments.

Despite the importance of this information and the problems noted above,the recordation or management of information relating to sterilizationin U.S. hospitals today usually includes several subjective, manualsteps. For example, forms are manually filled out with a pen or pencil,or a sterilization indicator is subjectively inspected for color change,or the information is manually typed into a database. When a hospitalutilizes several different types of sterilizers (e.g. steam sterilizers,flash steam sterilizers, ethylene oxide sterilizers or vapor phasehydrogen peroxide sterilizers), it makes the recording problem even morecomplex. To address the problems mentioned above, hospitals invest insignificant and costly training of personnel responsible forsterilization monitoring.

There are many sterilization article tracking systems reported in theliterature. U.S. Pat. No. 3,568,627 discloses a combined record card andsterilization indicator. German Utility Model (Gebrauchsmuster) No. G 9004 818.0 (assigned to Vereinigte Papierwarenfabriken GmbH) discloses alabel for sterile packaging. However, these require manual stepsassociated with the sterilization information tracking.

Bar codes are used extensively in the health care industry. See Adams etal., Bar Coding: An Effective Productivity Concept, JONA, Vol. 21, No.10 (October 1991); and Weilert et al., Putting Bar Codes to Work forImproved Patient Care, Clinics in Laboratory Medicine, Vol. 11, No. 1(March 1991). German Patent Application No. DE 3917876 discloses a barcode on a surgical instrument. U.S. Pat. No. 5,635,403 describes atracking and identification card for an air filter specimen thatincludes a bar code. U.S. Pat. No. 5,653,938 discloses bar codes used ina method for ensuring sterility of surgical drapes. Such bar codescomprise a permanent, colorfast black ink, as opposed to a sterilizingagent sensitive ink (e.g. one that changes colors during a sterilizationcycle).

European Patent Application No. 630 820 discloses a process and systemfor monitoring material flow during the preparation of sterile goods.This inventory system utilizes bar codes to help track objects to besterilized. U.S. Pat. Nos. 5,374,813 and 5,610,811 describe surgicalinstrument tracking systems that make use of bar codes. None of thesebar codes include a sterilizing agent sensitive ink.

Some hospitals utilize computerized inventory management systems thatrequire a user to manually key in data relating to the status of asterilization indicator. For example, in the same sterilization load, abiological indicator, chemical indicators and a test pack may be used.The prior art inventory management systems require the user to manuallyinput a great deal of data relating to these different types ofsterilization indicators with the attendant risk that the user willimproperly record the information or fail to record it at all. Forexample, a user may manually type in information relating to whether theindicator shows “pass” or “fail” of the sterilization cycle. Thedifficulty associated with accurately recording sterilizationinformation is exacerbated by the fact that chemical indicatorinformation is typically recorded just after a sterilization cycle whilebiological indicator information is recorded many hours or days afterthe sterilization cycle.

The art is also replete with electro-optical devices for reading items.Examples of such devices are described in U.S. Pat. Nos. 5,351,078;5,576,528 and 5,619,029. Canadian patent No. 1,204,300 (Prusik et al.)describes an electro-optical device for reading a bar code. The bar codeis said to be useful for, inter alia, assessing time-temperatureexposures of environmental indicating devices that are attached toproducts which experience progressive quality changes as they aresubjected to certain temperatures over certain periods of time. Prusiket al. does not disclose a chemical indicator for use in monitoring asterilization procedure at a health care facility.

Sterilization indicators and labels for articles to be sterilized aretypically manufactured at a location remote from their actual use. Thus,the type and design of sterilization indicators are dictated by themanufacturer, not by users. Moreover, users do not have the ability togenerate their own indicators. As a result, hospitals today are requiredto order and ship very specific types of indicators that are nothospital/site specific. There is little chance for customization of theindicator at the hospital. As a result, some hospitals even customizeinformation on existing labels with manual printable pens to captureinformation such as pack content, intended location and targeted use.

SUMMARY OF THE INVENTION

The present invention comprises a sterilization indicator and monitoringmethod that affords the user the ability to: a) acquire, store and usesterilization monitoring information quickly and cost effectivelywithout the delay, cost and inaccuracy associated with prior artsterilization indicators, b) reduce sterile products inventory holdtime, increase the accuracy of information storage and provide higherlevels of accuracy in data management, c) possess a unified, integratedsterility assurance and inventory management system, d) minimize thepotential for human error in a system for monitoring the sterilizationof articles, and e) customize sterilization assurance information forsite specific needs.

In one aspect, the present invention comprises a method of monitoringthe efficacy of a sterilization process comprising the steps of 1)subjecting a chemical indicator to a sterilization process, the chemicalindicator comprising: i) a substrate having a surface, and ii)sterilizing agent sensitive indicia associated with said surface of saidsubstrate, the indicia having: (a) a first state prior to being exposedto the sterilization process, and (b) a second state after being exposedto said sterilization process, wherein the first state is different thansaid second state, and at least said second state is machine readable;and 2) scanning the indicia of the chemical indicator with a machine toobtain information relating to the adequacy of the sterilizationprocess.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be further described with reference to theaccompanying drawing wherein like reference numeral refer to like partsin the several views, and wherein:

FIG. 1 is a schematic view of the present invention showing a containerpack with a sterilization indicator code being placed into a sterilizer;

FIG. 2 is a schematic view showing the container pack of FIG. 1 beingremoved from the sterilizer and placed into storage;

FIG. 3 is a block diagram of an example of a healthcare facility'ssterilization assurance system;

FIG. 4 is a schematic diagram of an integrated electronic articletracking and sterilization assurance system according to one aspect thepresent invention showing a personal computer, an optional mainframe orcentral computer, printer; scanning means, hardware for transmittingsterilization assurance information and objects to be scanned;

FIG. 5 is a schematic side view of one embodiment of a construction of asterilization indicator according to one aspect of the presentinvention;

FIG. 6 is a graph showing three spectral scans of sterilizationindicators subjected to different degrees of exposure to a sterilizationprocess, which scans were made at a 90 degree illumination incidenceangle;

FIG. 7 is a graph showing three spectral scans of the sterilizationindicators of FIG. 6, which scans were made at a 45 degree illuminationincidence angle;

FIG. 8 is a graph showing five spectral scans of sterilizationindicators subjected to different degrees of exposure to a sterilizationprocess, which scans were made at a 90 degree illumination incidenceangle;

FIG. 9 is a graph showing four spectral scans of the sterilizationindicators of FIG. 8, which scans were made at a 45 degree illuminationincidence angle;

FIG. 10 is a graph showing four spectral scans of sterilizationindicators subjected to different degrees of exposure to a sterilizationprocess, which scans were made at a 90 degree illumination incidenceangle;

FIG. 11 is a graph showing four spectral scans of the sterilizationindicators of FIG. 10, which scans were made at a 45 degree illuminationincidence angle;

FIG. 12 is a graph showing four spectral scans of sterilizationindicators subjected to different degrees of exposure to a sterilizationprocess, which scans were made at a 90 degree illumination incidenceangle;

FIG. 13 is a graph showing four spectral scans of the sterilizationindicators of FIG. 12, which scans were made at a 45 degree illuminationincidence angle;

FIG. 14 is a perspective view of an ink jet printer cartridge for use inone aspect of the present invention;

FIG. 15 is a schematic illustration of the test set up used to acquirethe graphs of FIGS. 7, 9, 11 and 13;

FIG. 16 is a schematic illustration of the test set up used to acquirethe graphs of FIGS. 6, 8, 10 and 12;

FIG. 17 is a schematic illustration showing components of a reader foruse in conjunction with the present invention;

FIG. 18 is a schematic illustration of one embodiment of the componentsof the reader of FIG. 17;

FIG. 19 is a flowchart showing one example of the logic associated withthe processor of FIG. 18;

FIG. 20 is a schematic drawing showing the elements of another exampleof a processor component of a reader according to the present invention;

FIG. 21 is a view of a computer screen of an example of a sterilizationmonitoring tracking system according to an aspect of the presentinvention;

FIG. 22 is a view of a computer screen of the sterilization monitoringtracking system of FIG. 21 after “sterilizers” has been selected;

FIG. 23 is a view of a computer screen of the sterilization monitoringtracking system of FIG. 21 after “Status of Articles to be Sterilized”has been selected;

FIG. 24 is a view of a computer screen of the sterilization monitoringtracking system of FIG. 21 after “Sterilization Indicators” and aparticular type of sterilization procedure have been selected;

FIG. 25 is a view of a computer screen of a sterilization monitoringtracking system which identifies a particular pack to be subjected to asterilization procedure, the contents of the pack, and steps to occurduring a sterilization monitoring process;

FIG. 26 is a view of a computer screen of a sterilization monitoringtracking system showing an example of a warning and further instructionsthat may be provided to a user;

FIG. 27 is a view of a computer screen of a sterilization monitoringtracking system that allows a user to create his or her own chemicalindicator or to obtain information relating to sterilization indicatorselection;

FIG. 28 is a view of a computer screen of a sterilization monitoringtracking system showing a particular item's sterilization history;

FIG. 29 is a view of a computer screen of a sterilization monitoringtracking system showing steps associated with automatically reading achemical indicator;

FIG. 30 is a view of a computer screen showing an example of a screenfor use in customization of a chemical indicator;

FIG. 31 is a view of a computer screen showing an example of a screenfor use with a device for automatically reading the results of abiological indicator;

FIG. 32 is a top view of an embodiment of a sterilization indicatoraccording to the present invention prior to being subjected to asterilization cycle; and

FIG. 33 is a top view of the sterilization indicator of FIG. 32 afterthe indicator is subjected to a sterilization cycle.

DETAILED DESCRIPTION

Referring now to FIGS. 1 and 2, there is shown a preferred embodiment ofsterilization indicator or monitor 10 according to the presentinvention. The sterilization indicator 10 monitors the effectiveness ofa sterilization process provided by sterilizer 20.

The sterilizer 20 can conduct any one of a wide variety of sterilizationprocesses including those sterilization procedures that utilizedifferent sterilizing agents such as hydrogen peroxide, peracetic acid,glutaraldehyde, ozone, steam, dry heat, ethylene oxide, formaldehyde,and gamma irradiation as a sterilant or as an element in a step in theprocedure, and those sterilization procedures which utilize combinationsof such sterilizing agents. The present invention may be practiced withprocedures that utilize matter in a variety of states such as liquids,gases, fluids, plasmas and sterilization procedures that utilizecombinations of those states. For example, the sterilizer 20 may utilizehydrogen peroxide. As used herein, vapor phase, liquid phase and plasmahydrogen peroxide sterilization procedures are all within the broaddefinition of hydrogen peroxide sterilization procedures. Sterilizationprocedures that utilize hydrogen peroxide as merely a component during asubstantial portion of the procedure are also included within themeaning of the phrase “hydrogen peroxide sterilization procedure”. U.S.Pat. Nos. 4,169,123; 4,169,124; 4,642,165; 4,643,876, 4,744,951;4,756,882; 4,943,414; and 5,667,753 all describe hydrogen peroxidesterilization procedures and the entire contents of each of them areherein incorporated by reference.

The sterilization indicator 10 is preferably capable of being read by acode reader (e.g. a bar code reader). The sterilization indicator 10comprises a substrate or backing having a surface 17, and sterilizingagent sensitive means 25 (see FIG. 2) for responding to a sterilizationprocess. The sterilizing agent sensitive means 25 could be white inkprinted on the surface 17 of a white substrate at a predeterminedposition and pattern. The ink is preferably sized, shaped and orientedin a predetermined manner, such as a portion of a bar code. The inkcould be designed to change its initial white color to black after asterilization procedure.

As used herein, “sterilizing agent sensitive means for responding to asterilization process” means a composition that is capable of having afirst indicating state prior to being exposed to a predeterminedsterilization procedure and a second indicating state after exposure toat least a portion of the sterilization procedure (preferably the entiresterilization procedure). Preferably, the first indicating state of thecomposition is a first color and the second indicating state of thecomposition is a second color that is different than the first color.The first state could also be a substantially clear or transparent ortranslucent state, and the second state could be a substantially opaqueor colored state. The converse of these states could also be employed.

FIGS. 32 and 33 show an alternative embodiment of the present invention.FIG. 32 is a top view of a sterilization indicator 2 prior to beingsubjected to a sterilization cycle in sterilizer 20 (FIG. 1). In thesterilization indicator 2, the sterilizing agent sensitive means forresponding to a sterilization process comprises a tablet 5 that wicksalong a backing 3 using the components of the indicators described inU.S. Pat. Reexamination Certificate No. B1—3,981,683, (Larsson et al.)and U.S. Pat. Reissue No. 34,515 to Foley (the entire contents of thefile histories of the patents, the Reexamination and Reissue are hereinincorporated by reference).

The top of the indicator 2 includes a surface 8 with a cutout or window4 that is in the size and shape of a bar code. The frame of the window 4is the appropriate size or shape (e.g. width) so that the sterilizationindicator 2 may be read by a code reader after sterilization. However,because the backing 3 is substantially the same color as the surface 8(e.g. white), the bar code is initially substantially indescernibleprior to being subjected to a sterilization process.

FIG. 33 is a top view of the sterilization indicator 2 after it issubjected to a sterilization cycle. The tablet 5 has melted and wickedalong backing 3. When melted, the tablet 5 is a different color than thebacking 3. As a result, the bar code 9 becomes readable by a reader dueto the color of the melted tablet 5.

Optionally, the sterilization indicator 2 could include a bar code 17printed from a colorfast, permanent ink that can be used for inventorypurposes. The indicator 2 may also include other indicia 1.

There are a wide variety of suitable indicating compositions for use inconjunction with the variety of sterilization procedures mentionedabove. Suitable compositions (and other components) for thesterilization indicator 10 are described in U.S. Pat. Nos. 2,118,144;2,937,279; 3,098,751; 3,258,312; 3,311,084; 3,360,337; 3,360,338;3,360,339; 3,386,807; 3,523,011; 3,627,469; 3,667,916; 3,684,737;3,852,034; 3,862,824, 4,155,895; 4,138,216; 4,015,937; 4,094,642;4,165,399; 4,166,044; 4,179,397; 4,168,779; 4,188,437; 4,240,926,4,382,063, 5,057,433; 5,064,576; 5,087,659; 5,451,372; and 5,316,575(the entire contents of each of which are herein incorporated byreference). UK Patent Nos. 1458533 and 1370470 and PCT publication no.98/13431 also disclose suitable compositions and backings for thepresent invention (the entire contents of each of which are hereinincorporated by reference). The literature also describes suitablecompositions. See Royce and Bower, “An Indicator Control Device forEthylene Oxide Sterilization.” J. Pharm. and Pharm. 11, Suppl.294T-298T, and Brewer et al, Journal of Pharmaceutical Sciences, pages57-59, January 1966.

As an example for steam sterilization, there are a number of compoundshaving sulfur-containing radicals that will decompose (e.g. to metalsulfide) under steam sterilization conditions with a pronounced colorchange. Metal sulfides tend to be strongly colored and are often themost stable form of metal sulfur-containing compounds. Furthermore, theyare often insoluble in water and may be held in a binder to preventstaining. The preferred sulfur-containing radical is thiosulfatealthough other groups may be employed, e.g., polythionates, etc.Compounds for use as the primary color change component include:

lead thiosulfate which is white in color and decomposes to yield blacklead sulfide under steam sterilization conditions,

copper thiosulfate which is yellow in color and decomposes to yieldblack copper sulfide under steam sterilization conditions,

ferrous thiosulfate which is light green in color and decomposes toyield a black sulfide under steam sterilization conditions,

nickel thiosulfate which is light green in color and decomposes toblack/green nickel sulfide under steam sterilization conditions,

cobalt thiosulfate which is light red/purple in color and decomposes todeep purple/black cobalt sulfide under steam sterilization conditions,

bismuth thiosulfate which is orange/brown in color and decomposes toblack bismuth sulfide under steam sterilization conditions,

chromium thiosulfate which is gray/blue in color and decomposes to darkgreen chromium sulfide under steam sterilization conditions, and

silver thiosulfate which is brown in color and decomposes to blacksilver sulfide under steam sterilization conditions.

Precursors of such sulfur-containing compounds may be used that willyield the sulfur-containing compounds under aqueous conditions. Forexample, lead carbonate and sodium thiosulfate may be employed as thecolor change component in the ink. These compounds undergo a doubledecomposition reaction to yield lead thiosulfate under aqueousconditions. During the steam sterilization cycle, lead thiosulfate isinitially formed which then decomposes to lead sulfide providing thedesired color change.

In the case of an ethylene oxide sterilization process, ethylene oxideis sometimes diluted with a gas inert to the ethylene oxide, such asFreon®, a fluoro-chloro substituted ethane, or CO₂. The Freon(g selectedshould be a gas at the sterilization temperature. The concentration ofethylene oxide could be about 450 mg/liter to about 1,500 mg/liter,while processing temperatures can range from about 70 to about 140° F.Preferably, where the diluent is Freon®, the ethylene oxideconcentration is about 12 wt. % in the sterilant gas. Where the diluentis CO₂, the concentration of ethylene oxide is about 10 wt. %. For suchprocesses, the parameters which affect ethylene oxide sterilizationprocesses are exposure time, ethylene oxide concentration, temperatureand humidity. For diluted ethylene oxide, relative humidities below 30%RH limit the effectiveness of the ethylene oxide sterilization process.High humidities, e.g., above 90% RH, also results in inadequateprocessing.

Sterilizing agent sensitive means 25 (FIG. 2) comprising4(4-nitrobenzyl)pyridine may be used in ethylene oxide sterilizationprocess monitoring. See, for example, Journal of PharmaceuticalSciences, Brewer et al., pages 57-59, January 1966. Other compounds,including pyridines and quinolines, have also been utilized.

The sterilization indicator 10 may also be one designed for use in ahydrogen peroxide sterilization procedure (e.g. the procedure providedby the Sterrad® Hydrogen Peroxide Plasma Sterilizers available fromAdvanced Sterilization Products of Irvine, Calif. U.S.A. Examples ofindicating compositions for use in hydrogen peroxide sterilization maybe found in European Patent Application Publication No. 914 833, and PCTInternational Publication Nos. 98/52621; 96/33242 and 98/46994 (theentire contents of each of which are herein incorporated by reference).

Alternatively, the sterilization indicator 10 may be used in asterilization process that includes the use of a peracetic acid (e.g.the STERIS SYSTEM 1™ and Steris 20™ Sterilant Concentrate available fromSteris of Mentor, Ohio U.S.A.). Suitable indicating compositions aredescribed in PCT International Publication No. PCT/WO/98/58683 (theentire contents of which are herein incorporated by reference).

In the case of a liquid peracetic acid sterilizer 20, means 25 (FIG. 2)preferably includes a halide salt that, when subjected to an oxygensource, is oxidized to release a free halide. The free halidehalogenates a dye causing it to change from a first color to a secondcolor. The preferred halide is a salt of an alkali or alkaline earthmetal, e.g., potassium bromide. A suitable dye is phenol red, preferablythe sodium salt thereof.

The combination of dye and the alkali metal or alkaline earth halide maybe applied to a substrate in a suitable medium (e.g. by flexographicprinting). The substrate may optionally be any substrate through whichthe sterilant can diffuse. Exposure of the substrate to thesterilization process should not adversely affect the sterilizationprocess by, for example, excessively absorbing sterilant. Polymericmaterials or coatings are useful to prevent excessive absorption ofsterilant. For convenience of use, the substrate could be an elongatedstrip of material with the indicator composition printed in a bar codeat one end. This allows the remainder of the strip to act as a handle bywhich the indicator can be held.

Indicating compositions for a peracetic acid sterilizer 20 may comprisea colorant susceptible to halogenation. Such an indicating ink maycomprise fluorescein and/or phenol red. When phenol red is used as thedye and a bromine salt is used, the pH of the paper is preferably atleast 5.0, preferably at least 5.2. This is because the bromophenol blueformed has a pK of about 4. Below 4, the bromophenol blue is yellow, andabove 4 the dye is blue. The phenol red, on the other hand, has a pK ofabout 7.9. The pH of the paper, which is to have a yellow starting colorwhere the dye is phenol red, can be about 5.0 to about 7.5. Where thispH range is used, the pH is fortuitously above the pK of the bromophenolblue, and, hence, the bromophenol blue formed where a bromide is thehalide will have a blue appearance. The contrast between the initialyellow color of the phenol red and the final blue color of thebromophenol blue is sharp.

Illustrative non-limiting examples of alkaline earth halide salts usefulfor a sterilization indicator 10 for peracetic acid procedures includemagnesium bromide, magnesium chloride, and potassium bromide. Each saltshould be associated with a dye that can be halogenated by free halogenliberated by the reaction of halide with the peracetic acid. Theresulting halogenated dye should have a color that is distinguishablefrom the dye selected as the starting material to be halogenated. Dyeshaving those required characteristics can be readily selected based ontheir chemical properties. There are numerous reference books listingdyes and their chemistry, illustrative of which is H. J Conn'sBiological Stains, 8th Edition, Lillie, R. D., The Williams & WilkinsCo., Baltimore, Md. (1969) (incorporated herein by reference).

Illustrative nonlimiting examples of alkaline earth halide salts usefulfor a sterilization indicator 10 for peracetic acid procedures includemagnesium bromide, magnesium chloride, and potassium bromide. Each saltshould be associated with a dye that can be halogenated by free halogenliberated by the reaction of halide with the peracetic acid. Theresulting halogenated dye should have a color that is distinguishablefrom the dye selected as the starting material to be halogenated. Dyeshaving those required characteristics can be readily selected based ontheir chemical properties. There are numerous reference books listingdyes and their chemistry, illustrative of which is H.J Conn's BiologicalStains, 8th Edition, Lillie, R. D., The Williams & Wilkins Co.,Baltimore, Md. (1969) (incorporated herein by reference).

Dye Initial Color Color Change Ethyl Red Light Pink Light Yellow ThymolBlue Yellow-Orange Light Yellow Bromothymol Blue Yellow Yellow m-CresolPurple Faded Yellow Sky Blue Bromophenol Blue Yellow Light BlueBromocresol Purple Yellow Faded Yellow Bromocresol Green YellowYellow-Green Cresol Red Light Yellow Lighter Yellow

The sterilization indicator 10 may include any backing or substrate thatis compatible with the particular sterilization environment.Additionally, the substrate should be capable of withstanding thepredetermined sterilization environment. For example, in the case ofsteam sterilization conditions, the backing is preferably capable ofwithstanding a temperature of 110° C. to 142° C., in the presence ofsteam for a period of up to 30 minutes. Suitable substrates includepaper which may be absorbent or saturated with a rubber/resin solutionor a natural or synthetic latex, coated paper, card, plastics material,metallised material, metal foil, and non-woven or woven textilematerials. In the case of hydrogen peroxide sterilization procedures,the backing should not absorb excessive amounts of hydrogen peroxide.Excessive absorption of hydrogen peroxide can result in cycle shut downor an inaccurate sterilization indication by the sterilization indicator10.

Other suitable backings can be made from any non-water-dispersible film,paper, or other material physically capable of withstanding theconditions of a given sterilization cycle. Non-limiting examples ofother suitable backings include isotactic polypropylene backings, suchas disclosed in U.S. Pat. No. 4,898,762, as well as latex-saturatedpaper backings, foil backings, woven and non-woven backings,polyolefin-based film backings, such as polyethylene backings, and alsopolyester film backings. For example, a backing could comprise a 29pound basis weight Kraft paper (M-2383 Smooth Crepe Semi-Bleached KraftSaturating Paper; Mosinee Paper Corporation, Mosinee, Wis.). Otherbacking materials are disclosed in U.S. Pat. Nos. 4,301,195; 4,537,405;4,956,230 and 5,679,190 (the entire contents of which are hereinincorporated by reference).

Some sterilization indicators 10 may optionally include top coatings.The top coating could be substantially transparent and couldsubstantially prevent/minimize diffusion of reactive chemicals(chemicals which react mainly with the means 25 or affect therate/nature of reaction) in the atmosphere. The top coating is alsohelpful in reducing any harmful effect of other ambient conditions, suchas humidity, ultraviolet light, and pollutants. The top coat can becoated from solution/emulsion or laminated. A binder material can alsobe a top coat.

When the present invention refers to a sterilizing agent sensitive meansbeing associated with a substrate, it includes both situations where thesterilization indicator includes one or more coatings on top of theindicator composition as well as situations where the sterilizationindicator includes no coatings on top of the indicator compositions.Representative examples of the optional top coating are syntheticpolymers such as polyethylene, polypropylene, polyesters, polydienes,polyvinylacetate, polyurethane, polyamides, polyethyleneglycol,polystyrenes, polyacrylates, polyinethacrylates, polyacrylamides,polyvinylfluorides, fluorinated polymers and copolymers, polyvinylesters, teflons, polytetrafluoroethylenes, polyoxides, polycarbonates,polyvinylchloride, polysiloxanes, and natural polymers such asderivatives of cellulose and starch and gelatin and mixtures thereof.The selection of the top coating material is, of course, dependent uponthe sterilization environment because the top coating should preferablybe compatible with and capable of withstanding the sterilizationenvironment. Additionally, the top coating should not adversely affectthe second indicating state (e.g. color) of the means 25 aftersterilization nor should it interfere with detection by the reader.

The top coating material may be coated on the backing surface includingthe ink mixture by any conventional coating technology. Commontechnologies include air knife, brush, colander, cast coating, curtain,dip, extrusion, piezoelectric, continuous inkjet, blade, knife coating,gravure, kiss roll, off-set, reverse roll, rod, spray and squeeze roll,to name a few. See, Coeling, K. J. and Bublick, T. J., Encycl, Polym.Sci. Eng., Vol. 3, 552-615 (1986). One preferred method is screenprinting.

The identifying indicia or code may be formed from an ink mixtureincluding an ink composition, as described above, and at least oneoptional additive, such as a binder, a solvent or both. Upon applicationof the ink to the backing, the solvent evaporates leaving behind theactive ingredients bound together and to the substrate by the binder.

The optional binder should be compatible with the ink. One example of apreferred binder includes 24% nitrocellulose ethyl alcohol (HerculesInc., Wilmington, Del.); 3% phenol-formaldehyde resin (BECKCITE™ 24-102,BTL Specialty Resins, Toledo, Ohio); 9% tricresyl phosphate; 14% butylalcohol; 27% xylene, and 23% butyl acetate.

Optionally, the sterilization indicator 10 may comprise a label with asuitable adhesive. The sterilization indicator 10 shown in FIGS. 1 and 2is shown as a part of a label applied to a sterilization pack 12. Labelsare particularly useful in distinguishing packs 12 stored in a storagemeans 30, such as a shelf or cart. Suitable adhesives for labels for usein sterilization processes are described in Amhof et al., U.S. patentapplication Ser. No. 09/019,445 filed Feb. 5, 1998 (the entire contentsof which are herein incorporated by reference). Alternatively, thesterilization indicator 10 with a bar code can comprise a label placedon a bioligical indicator (e.g. the vial of a biological indicator).While the sterilization indicator 10 is suitable for use as a label orsterilization indicator tape, it is appreciated that the sterilizationindicator 10 can also be an indicator without an adhesive as well.

The sterilizing agent sensitive means 25 is preferably arranged in atleast a portion of a code. In FIG. 2, the means 25 forms a portion of abar code 14. In one embodiment of the present invention, the bar code 14may be partially formed of a permanent or colorfast ink (i.e. an inkthat is not sensitive to the sterilizing agent of a sterilizationprocess). In this embodiment of the present invention, a portion of thebar code remains substantially the same color both before and afterbeing exposed to a sterilization process.

In an alternative embodiment of the present invention, the entire barcode may be printed from sterilizing agent sensitive ink that changescolor upon exposure to a sterilization process. In this alternativeembodiment, the scanning device used to read the sterilization indicatoris preferably able to distinguish the first and second colors of the barcode. Depending on the use of the bar code, it may be useful (e.g. costeffective or otherwise convenient) to utilize a reader that can onlyread one of the two colors.

FIG. 1 shows the bar code 14 prior to being exposed to the sterilizationprocess within the sterilizer 20. In this embodiment, the portion of thebar code 14 that is formed of the colorfast or permanent ink provides afirst indication (e.g. “123456”) to a bar code reader prior to thesterilization indicator 10 being exposed to the sterilization process(FIG. 1). In the embodiment of the present invention shown in FIG. 1,the means 25 is not initially readable by the scanning means. The means25 is not readable prior to being subjected to a sterilization cycle.For example, the means 25 may comprise white sterilization indicator inkprinted on white paper.

The bar code 14 provides a second indication (e.g. “1234567”) to the barcode reader after the sterilization indicator 10 is exposed to asterilization process (FIG. 2). After the sterilization process, the barcode 14 includes a portion formed of an ink that is sensitive to thesterilization process and a portion formed from an ink that is notsensitive to the sterilization process. As can be seen by comparingFIGS. 1 and 2, after the sterilization process, the white sterilizationindicator ink has changed to black and added a bar on the bar code. Themeans 25 is now readable (after the sterilization cycle) and the barcode 14 now reads something different than it read prior to thesterilization cycle.

While the first indication (FIG. 1) provided by the sterilizationindicator 10 is different than the second indication (FIG. 2), thepresent invention includes embodiments where the first or second stateis not readable by a scanning means or bar code reader. For example, theentire bar code could optionally be comprised of a white to black steamsensitive indicator ink printed on a white background. Thus, it isappreciated that all or just a portion of the code may be formed fromthe sterilization agent sensitive means 25.

The sterilization indicator 10 may optionally include other forms ofsterilizing agent sensitive inks. FIG. 1 illustrates an optional symbol15 that substantially disappears or becomes substantially less prominentafter a sterilization cycle. For example, the symbol 15 can be the word“NOT” printed in steam sensitive indicator ink that is initially red ona white backing. Upon exposure to a steam sterilization cycle, the inkof this embodiment of the present invention changes to a color close tothe color of the backing (see FIG. 2) or clear.

As used herein, the term “code” means a predetermined image or symbolthat is sized and shaped to be read by a predetermined code reader (e.g.a bar code reader), as opposed, for example, to the bar of indicatingink found on some prior art chemical indicators. The predetermined codereader is capable of reading and decoding the symbol of the code. Whileapplicants have discovered that prior art chemical indicators may beread by specialized color reading devices (discussed in greater detailbelow), the prior art sterilization indicators do not includesterilization sensitive inks printed in a predetermined image or symbolthat are sized and shaped to be read by a predetermined code reader.

Examples of suitable codes for use in the sterilization indicator 10include one and two dimensional codes, bar codes, linear codes, matrixcodes, discrete codes, fixed and variable length codes. An example of asuitable variable length code is Code 39. A suitable fixed length codeis the Universal Product Code (UPC).

The phrase “bar code” means a symbol that is a pattern of indicia(preferably alternating parallel bars and spaces of various widths) thatrepresents data elements or characters. For example, the bars couldrepresent strings of binary ones (1's) and the spaces represent stringsof binary zeros (0's).

The code can be printed in a variety of fashions including the use ofdot-matrix printers, thermal printers, thermal transfer printers, inkjet printers and laser printers. Ink formulations may be printed by arange of printing techniques, e.g., flexographic, rotogravure, inkjetand screen printing, etc.

A sterilization indicator 10 that includes a code may be constructed tobe any of the five classes of chemical indicators found in Sterilizationof health Care Products—Chemical Indicators—Part 1: GeneralRequirements, ANSI/AAMI ST 60-(1996) (incorporated herein by referencein its entirety). For example, the sterilization indicator 10 maycomprise a process indicator for steam sterilization and the componentsof the sterilization indicator 10 may be selected so that thesterilization indicator 10 satisfies the 121 degree Celsius test definedin Section 6.1 of the Sterilization of health Care Products—ChemicalIndicators—Part 1: General Requirements, ANSI/AAMI ST 60-(1996)(referencing the test methods described in ANSI/AAMI ST 45—1992,Bier/Steam vessels, which test methods are herein incorporated byreference) in that:

a) after exposure to a previously stabilized condition of dry heat at140 degrees Celsius (plus or minus two degrees Celsius) for 30 minutes(plus or minus one minute), the sterilization indicator 10 shows eitherno change or a change that is markedly different from the changeoccurring after exposure to the steam sterilization process; and

b) the second indication (e.g. the second color) shall not occur untilthe sterilization indicator has been exposed to saturated steam for notless than 2 minutes at 121 degrees Celsius (+3/−0 degrees Celsius); and

c) the second indication shall occur after the sterilization indicatoris subjected to saturated steam for not more than 10 minutes at 121degrees Celsius (+3/−0 degrees Celsius).

The components of the sterilization indicator 10 may also be selected sothat the sterilization indicator 10 satisfies the 134 degree Celsiustest defined in Section 6.1 of the Sterilization of health CareProducts—Chemical Indicators—Part 1. General Requirements, ANSI/AAMI ST60-(1996) (again referencing the test methods described in ANSI/AAMI ST45—1992, Bier/Steam vessels) in that:

a) after exposure to a previously stabilized condition of dry heat at140 degrees Celsius (plus or minus two degrees Celsius) for 30 minutes(plus or minus one minute), the sterilization indicator shows either nochange or a change that is markedly different from the change occurringafter exposure to the steam sterilization process; and

b) the second indication shall not occur until the sterilizationindicator has been exposed to saturated steam for not less than 20seconds at 134 degrees Celsius (+3/−0 degrees Celsius); and

c) the second indication shall occur after the sterilization indicatoris subjected to saturated steam for not more than 2 minutes at 134degrees Celsius (+3/−0 degrees Celsius).

Optionally, for purposes of steam sterilization, the components of thesterilization indicator 10 may be selected so that it satisfies both the121 degree Celsius test and the 134 degree Celsius test defined inSection 6.1 of the Sterilization of health Care Products—ChemicalIndicators—Part 1: General Requirements, ANSI/AAMI ST 60-(1996). In thecase of a sterilization indicator 10 for an ethylene oxide sterilizationprocess, the ANSI/AAMI guidelines include tests for ethylene oxidesterilization processes. Sterilization of health Care Products—ChemicalIndicators—Part 1: General Requirements, ANSI/AAMI ST 60-(1996)references test methods described in ANSI/AAMI ST 44-1992 BIER/EO gasvessels, which test methods are herein incorporated by reference. Thesterilization indicator 10 could be constructed to meet the guidelinesfor ethylene oxide sterilization processes as well.

The sterilization indicator 10 may optionally comprise an integratingindicator. That is, the chemical indicator 10 is constructed so that itreacts to all critical parameters over a specific range of apredetermined sterilization process. For a steam sterilization process,the critical parameters are time, temperature and saturated steam.

In another aspect of this invention, it has been determined thatspecialized scanning means are capable of reading sterilizationindicators that do not have sterilizing agent sensitive means arrangedin a code. As used in this specification, the phrase “scanning means”means an automatic device or machine capable of detecting first andsecond indicating states of a sterilization indicator. For example, thescanning means may be capable of reading the first and second states ofthe sterilizing agent sensitive means of a chemical indicator, or firstand second readings from a biological indicator.

A “code reader” is an automatic device or machine capable of reading anddecoding the symbols of a predetermined code. Thus, a code reader is aspecialized form of a scanning means.

With some specialized scanning means of the present invention, thesterilizing agent sensitive means need not be in code form. Thus,“scanning means” according to the present invention includes devicesthat are capable of reading a sterilization sensitive ink composition incode form and also devices that are capable of reading a sterilizationsensitive ink composition in non-code form (e.g. with the ink printed ina rectangle as used with some prior art sterilization indicators).Preferably, the scanning means is an electro-optical device.

FIG. 17 schematically illustrates components of a preferred embodimentof scanning means according to the present invention. The scanning meanscomprises an illumination source 82, a controller/processor 81, adetector 83 and an output component 84.

The illumination source 82 may provide any suitable source of energysuch as radiation, light or other suitable beam. The detector detectsenergy reflected from the sterilization indicator 10.

The output component 84 may be any suitable means known in the artincluding but not limited to display lights, computer displays,graphical user interfaces or further communication to additionalelectronic hardware.

The controller/processor 81 receives information from the detector 83and optionally the output component 84. The controller/processor 81 iscapable of controlling the components of the scanning means. If thescanning means is a code reader, the processor 81 is capable of readingand decoding the code of the sterilization indicator 10. If thesterilization indicator 10 does not include a code, the scanning meansshould be capable of distinguishing the appearance of the sterilizationindicator 10 before and after it is subjected to a sterilization processin sterilizer 20.

The scanning means for use with the present invention includes codereaders and even specially adapted non-code readers. Code readers forreading bar or matrix codes include contact and non-contact fixed beamscanners, moving beam scanners, handheld scanners, fixed mount scanners,and laser and solid state imagers such as charge-coupled devices.

A scanning means comprising a laser scanner may include a visible laserdiode for emitting a laser beam, a scanning element (e.g. an oscillatingmirror for sweeping the laser beam in a horizontal and/or raster likepattern across the bar code), and receiving optics including aphotosensor for sensing the light reflected off the target bar code andconverting the light energy into an analog electrical signal, theamplitude of which corresponds to the reflectivity of the target barcode. The device reads the analog signal by processing it, digitizing itand decoding it into data representative of the data that had beenencoded into the target bar code. The scanning means is preferably onethat is capable of reading and decoding the coded information from thesterilization indicator 10.

In yet another embodiment, the scanning means may comprise a chargecoupled reader. A charge-coupled bar code reader can be aone-dimensional or two-dimensional device. A one-dimensional device usesa linear array of photosensors to acquire an image of the cross-sectionof the entire linear bar code at once. The device produces an analogwaveform whose amplitude mimics the darkness and lightness of the barsand spaces of the captured image. Electric charge stored in each of theelements of the charge-coupled device array as a function of the amountof light sensed by an area covered by each element is shifted outserially to form electric signals for processing, digitizing anddecoding. Two-dimensional devices function in a similar fashion tocapture the entire image of a two-dimensional bar code symbol at once.

The code readers and scanning means associated with the presentinvention may also comprise any of the reading devices disclosed inGreene, Production and Inventory Control Handbook, 3^(rd) Edition,McGraw-Hill, New York, (1997), and Longe et al., Bar Code Technology inHealth Care: A Tool For Enhancing Quality, Productivity and CostManagement, Advanstar Communications, ISBN 0-929870-20-4, Library ofCongress Catalog Card No. 93-71570 (1993) (the entire contents of eachof which are herein incorporated by reference).

In yet another embodiment of the present invention, the scanning meanscomprises a densitometer. Typically, a densitometer includes a filter toselectively read and enhance desired colors. To decode the informationin a bar code, a small spot of light is passed over the bars and spacesvia a scanning device. The bar code will reflect light back into thescanner in various amounts after passing through a filter. The filtercould be chosen with preference given to the second color of theidentifying indicia used in an automatic reading system of the presentinvention. As a result, the contrast can-be enhanced, thereby improvingreadability of the bar coded data. The differences in reflections aretranslated into electrical signals by a light detector in the scanner.This type of reading device may be particularly preferred where the barcode 14 is comprised entirely of a sterilizing agent sensitive ink thatchanges from one color (e.g. purple) to another color (e.g. green).

It has been found that the surface reflectivity of some steamsterilization sensitive inks varies greatly, even for the same type ofink. For example, the gloss of a particular ink can vary from lot tolot. Top coatings on chemical indicators often have the effect ofscattering incident light making an automatic reading of the chemicalindicator more difficult. It has been determined that the angle betweenthe illumination source of the scanning means and the sterilizationindicator ink influences the character of the reflection from thesterilization indicator ink. General chromatic insensitivity of someconventional barcode readers make them less appropriate for reading somechemical indicators.

FIG. 15 is a schematic illustration of a scanning means used to scan achemical indicator 70. A chemical indicator includes a backing 75, asterilant sensitive ink coating 74 and an optional top coating 73. Thescanning means includes illumination source 71 and detector 72.

The illumination source 71 directs energy toward the surface of thechemical indicator 70. The detector 72 collects energy reflected fromthe surface. The illumination source 71 preferably provides light at anangle (theta 1) of incidence with the surface. The angle theta one (FIG.15) is preferably more than approximately ten degrees and less thanninety degrees in order to improve the character of the reflectance fromthe chemical indicator 70.

FIG. 16 illustrates an arrangement where the illumination source 71provides light at an angle normal to the surface of the chemicalindicator 70. This is not a preferred arrangement of the illuminationsource 71, chemical indicator 70 and detector 72 as the character of thereflection from the chemical indicator 70 is often quite poor,especially when the chemical indicator 70 has a glossy top coat 73.

Preferably, the scanning means of the present invention includes apositioning means for positioning the surface of the chemical indicator70 relative to the illumination source 71 and the detector 72. Thishelps control the quality of the reflected light from the chemicalindicator 70. The positioning means may comprise a guide, framework oran automatic feeding device such as those found in office copiers.Optionally, the sterilization indicator (e.g. 10) could have positioningindicia or a symbol printed thereon that the reader is programmed toseek in order to properly position the illumination source 71, detector72 and the chemical indicator. The illumination source 71 and detector72 could also be made movable relative to the framework of the reader tohelp ensure proper orientation.

FIG. 18 is a detailed block diagram of one embodiment of the scanningmeans of FIG. 17. The device is particularly suitable for reading andinterpreting colormetric chemical indicators 10 that do not includesterilization ink in a code form. As discussed above, the apparatus maybe described as having generally three components, illuminator 82,detector 83, and controller 81.

In a preferred embodiment, the illuminator 82 has three sources oflight, preferably light emitting diodes. Red, green and blue diodes areshown. The current of each diode is set by the controller 81 through theuse of a digital to analog converter. The three sources couple lightinto an optical mixer (waveguide) where the three primary emissions arehomogenized and delivered to the chemical indicator 70. A portion of thelight may optionally be fed back to a broadband detector 83, whichallows closed loop servo control of the sources. The controller 81receives information from the illumination source 82 and detector 83 vialines 88 and 89. Preferably, the illumination source 82 is capable ofscanning through a variety of wavelengths of light. Also preferably, thedetector 83 is sensitive in a substantially repeatable fashion to avariety of light sources.

Light from the exit aperture of the waveguide is allowed to interactwith the sterilization indicator under scrutiny 70 and is collected bythe detector 83.

The controller 81 sweeps through an appropriate spectrum of light bymodulating the three color sources. At each significant compositewavelength the controller quantifies the output from the detector 83.Sample points may be predetermined as a function of the model chemicalindicator 70 that is being scanned.

FIGS. 19 and 20 are examples of embodiments of a processor/controller81. In FIG. 20, upon spectrally scanning the chemical indicator 70 underscrutiny (see FIG. 20), the processor 81 stores the data 92 from theindicator 70. Typical spectral curve data 91 for the type of indicatorunder scrutiny may be included in the storage means (e.g. non-volatilememory) of the processor 81. The data 92 from the indicator 70 may becompared against the spectral curve data 91 from that type ofsterilization indicator (e.g. the information that was previously loadedinto non-volatile memory). Thresholding 93 may be accomplished bycomparing for best matches with known spectral curve data 91.

As discussed above, the processing means 81 can optionally includenon-volatile memory that includes reference data. The reference data mayinclude data generated from sterilization indicators that have beenexposed to varying degrees of a sterilization process. Various spectralcurves may be generated for chemical indicators exposed to differentlevels of a sterilization process. As another feature, various spectralcurves may be generated for chemical indicators subjected tosterilization cycles suffering from common sterilizer failure modes.Spectral tolerancing and limits bands may be established to compensatefor production variations for a particular type of chemical indicator.These established spectral curves for a particular type of sterilizationindicator may be downloaded into the nonvolatile memory of the reader orscanning means at the time of manufacture or could be otherwise includedin a computer means. As new types of chemical indicators becomeavailable, the new spectral curves and model numbers may be downloadedto the scanning means/reader/computer.

In this embodiment, the processing means 81 includes means for comparinginformation generated from the chemical indicator 70 with referencedata. The reference data may comprise reference spectral curves for theparticular type of chemical indicator. For example, if the scanningmeans is attempting to read a 3M Comply (SteriGage) Steam ChemicalIntegrator No. 1243A, it can be programmed to open a reference filecontaining information taken from reference indicators that weresubjected to varying degrees of a sterilization process and/or a lethalsterilization cycle and/or a sterilization process exhibiting a knownsterilizer failure mode. For example, to construct the reference file,several 3M Comply (SteriGage) Steam Chemical Integrators may besubjected to partial steam cycles that satisfy only two of the threecritical parameters of a steam sterilization cycle (e.g. time,temperature and steam). This reference data can be used to assist thescanning means in identifying 3M Comply (SteriGage) Steam ChemicalIntegrators that indicate that an inadequate sterilization cycleoccured.

After scanning the chemical indicator 70 under scrutiny to create aspectral curve, the scanning means may compare this scan against thefile with the reference spectral curves for the particular type ofchemical indicator. In the nonvolatile memory file, there will be aplurality of reference curves, which may be correlated to a specificsterilant exposure level or particular failure mode as discussed above.

The processing means may optionally include means for determining thecharacter of the sterilization process. For example, the scanning meansmay compare the curve generated from the chemical indicator underscrutiny and curves in the non-volatile memory and determine the bestmatch. Optionally, the scanning means may assign a sterilant exposurevalue to the curve generated from the chemical indicator 70 underscrutiny. This value may be compared against a pass/fail threshold.Appropriate information may then be indicated to a user.

The present invention is particularly suitable for use in an integratedelectronic record keeping and sterilization monitoring system. Such asystem can track medical supplies and devices throughout their lifecycle and can monitor the state (e.g. sterilized or contaminated) ofsuch supplies and devices.

The present invention includes a method of monitoring articles to besubjected to a sterilization process. The method includes the steps ofproviding a sterilization indicator capable of providing informationrelating to the efficacy of a sterilization process, an article to besubjected to the sterilization process, a reading device capable ofobtaining information from the sterilization indicator, and computermeans for processing information associated with the sterilizationindicator and the article. The method also includes the steps ofsubjecting the sterilization indicator and the article to thesterilization process, reading information from the sterilizationindicator with the reading device and associating information from thesterilization indicator with the article by the computer means. Anotheraspect of the present invention comprises a system of components (e.g.hardware and software) for use in an integrated sterilization monitoringand inventory tracking system.

FIG. 3 is a schematic view of a sterile processing system 200 in use ina hospital. New products 204 often need sterilization prior to use. Mostlarge hospitals have a central sterilization processing station 202. Thecentral sterilization station 202 often includes several different typesof sterilizers (e.g. steam and ethylene oxide). For example, newproducts 204 or heat sensitive articles can be sterilized within theirpackaging by an ethylene oxide sterilizer. Alternatively, severalinitially unpackaged articles can be collected and wrapped with opaquesterilization wrap to create what is known as a pack (e.g. see 12 inFIG. 2). The sterilization wrap is usually secured with indicator tape.Hospitals often place a chemical indicator within a pack as part of itssterilization monitoring procedures. Because the sterilization wrap isopaque, the chemical indicator within the pack cannot be read until theseal provided by the packing material is broken. However, once the sealis broken, the articles within the pack are no longer consideredsterile. Thus, sterilization wrap packs are not usually opened untilthey are placed in the operating room. Once an article is sterilized, itis moved to processed storage 208 to await its use.

Distribution 210 draws processed medical articles from storage 208 andorganizes them for use. For example, a kit for a particular type ofsurgical procedure may be assembled. The kit containing the sterilearticles is then sent and used in the operating room 214. If a pack isopened in the operating room 214 and the chemical indicator shows asterilization failure, delays and other undesirable consequences canresult.

Once used, the formerly sterile articles are sent to decontamination212. From decontamination 212, items are either discarded 216 or, if thedevice is reusable, the device may be sent to a clean room assembly 206.Once cleaned, the article can be sterilized again at centralsterilization 202.

FIG. 4 illustrates electronic components and architecture of an articletracking system for use with the present invention. The system can beused in an integrated sterilization information and inventory system.The system includes a personal computer 306, an optional mainframe orcentral computer 304, software, printer 308, and a scanning means suchas a bar code reader 312. The bar code reader preferably utilizes a handheld bar code reader 310 that can be separated from the base unit. Thesystem may optionally include electronic connection to a reader 329 fora chemical indicator that includes sterilization sensitive ink innon-code form 321, an automatic biological indicator reader 327 andhardware 328 for reading a sterilization indicator through an opaquepack wrap.

As shown by lines in FIG. 4, the various components of the system may beplaced in communication (e.g. electronic communication) by means such aselectronic wiring, wireless connections, internet or intranetconnections, and/or ethernet connections.

The article tracking system affords the health care practitioner theopportunity to input, monitor and store information about any device orsupply used within health care including information: a) provided bymanufacturers such as manufacturing dates, lots, regulatory information,shipping requirements, storage requirements, use and reuse conditionsand contraindications; b) added during distribution such as actualshipping and storage profiles, c) added within the health careinstitution including assignment of patient charge codes, inventorycodes, department codes, frequency of product use, date of product useand identification of practitioner actually using or prescribing theitem, d) retrieved from other devices such as electronic sterilizationtest packs, electronic sterilization integrators, electronic signalsfrom biological indicator readers 327, electronic signals from bar codereaders 312, and link components from multiple sources in a formatreflective of how the devices are actually used, and e) that previouslycould only be read at one location (e.g. the location of a sterilizationindicator) but which can now be read simultaneously at severallocations, even remote locations. As a result, the system improvesinventory management, cost management, reimbursement management, patientrecord management, and security management at the health care site.

Information from a device 327 for automatically reading the results of abiological indicator can optionally be connected to the computer 306 asa part of the system. U.S. Pat. Nos. 5,030,832; 5,063,297; 5,334,841 and5,863,790 and U.S. patent application Nos. 08/856,104, filed May 14,1997 and 08/967,747 filed Nov. 10, 1997 (the entire contents of each ofwhich are herein incorporated by reference) describe electronic readingapparatus for objectively reading fluorescence of biological indicators.These devices can be modified to provide information to the system ofthe present invention.

Unlike prior art systems, information from the reader 327 can be feddirectly to computer 306 without the need for a user to manually typethe results of the biological indicator into a sterilization monitoringor inventory system. The chance for human error in the system is therebyreduced.

FIG. 31 illustrates a simulated computer screen or graphical userinterface for the device 327 for automatically reading the results of abiological indicator. The device 327 may include a plurality of wells341 for receiving biological indicators, electro-optical components forreading the biological indicators and output components for sendinginformation relating to the biological indicators to a user. The outputcomponents may include a series of three lights for each biologicalindicator. A first light 342 may indicate whether a biological indicatoris properly seated in the corresponding well 341. A second light 343 mayindicate that the biological indicator within the corresponding wellindicates a failed sterilization cycle. A third light 344 may indicatethat the biological indicator within the corresponding well indicates alethal sterilization cycle. Optionally, the article tracking system (seeFIG. 4) of the present invention can receive electronic informationdirectly from the electronic biological indicator reader 327. Thus, theinformation from the biological indicator can be directly entered intothe article tracking system merely by having the user operate the reader327. There is no need to have the user take further steps to associateinformation from the reader 327 with the articles that were sterilizedwith the biological indicator.

The system may optionally include a reader 328 that is capable ofreading a sterilization indicator within an opaque pack. U.S. Pat. Nos.4,850,716 and 5,745,039 describe devices capable of reading asterilization indicator within a pack without the need for opening thepack. As shown in FIG. 4, information from the through-the-pack reader328 can be electronically supplied to computer 306. The user simplymachine reads the sterilization indicator with the reader 328 and thesterilization information is automatically fed to computer 306 withoutadditional opportunity for user recordation error. Early indication ofsterilizer failure is particularly helpful in that it reduces thechances that a pack 350 with non-sterile contents will enter thecarefully prepared and maintained sterile field found in the operatingroom 214 (FIG. 3).

FIGS. 21 through 30 are examples of computer screens that might beutilized in one embodiment of sterilization monitoring tracking systemaccording to one aspect of the present invention. The computer can beprogrammed to grant a user access to information relating to the statusof articles in the sterilization system of a hospital (see FIG. 3). Itcan also be linked to other databases used at the hospital includingsurgical demand and inventory management databases. As discussed in moredetail below, the computer program can also be used to customizechemical indicators to suit the particular needs of the hospital.

FIG. 21 is an example of a computer screen of a graphic user interfacefor a total sterilization management system. The user can select fromvarious options to obtain information relating to the sterilizationmonitoring activities of a health care facility. In the embodiment ofthe present invention shown in FIG. 21, the user could choose to manageor use information relating to the status of articles to be sterilized,such as the location or sterilization state (e.g. processed orunprocessed) of such articles. Alternatively, the user could choose toobtain information concerning sterilization indicators or thesterilizers themselves. Finally, the user could choose informationconcerning the contents or construction of a sterilization indicator,such as instructions relating to the creation of a sterilization pack.

FIG. 22 is an example of a computer screen of a graphic user interfacethat a user could encounter after selecting “sterilizers” in FIG. 21. Atthis point, a user could select information relating to suggestedsterilization indicators for use in the particular sterilization cyclesselected. Alternatively, the user could choose to construct his or herown customized chemical indicator for the preselected sterilizer.Optionally, a user could obtain additional information concerning thepreselected sterilizer such as proper loading instructions, loadingdensity, and contraindications. As an example, a particular sterilizermay not be approved by a regulatory agency for sterilization of certainarticles (e.g. surgical instruments with a lumen). The system may bedesigned to encourage uses of the sterilizer consistent with approveduses. It may even include means for preventing use of the sterilizeroutside its approved uses.

There is a position in the sterilization chamber of some sterilizersthat is known to be the most difficult point to sterilize. For somesterilizers, it might be near a drain, for other sterilizers, it may beanother location. Many regulatory guidelines call for a sterilizationindicator to be placed in the position in the sterilization chamber thatis known to be the most difficult position to sterilize. Once the userselects a particular sterilizer in FIG. 22, the system can optionallyprovide sterilization indicator placement information to the hospitalemployee. This could be in the form of an illustration showing theproper position.

FIG. 23 is a view of an example of a graphic user interface presented onthe computer screen after a user selects “Status of Articles to beSterilized” in FIG. 21. This screen could help a user track an item inthe sterilization system of a hospital. For example, a user in adistribution unit 210 of a hospital (FIG. 3) may need to know whetherthere are any sterile trocars at that location in order to assembletools for an upcoming sterilization cycle. This screen can help the userfind this information and identify its location. As another example,this information could be linked to a surgical demand database for useor exchange of information such as patient names, surgeon names,surgical procedure numbers and surgical procedure types.

FIG. 24 is a view of the graphic user interface screen after a userselects “Sterilization Indicators” in FIG. 21 and a particular type ofsterilization procedure (e.g. a steam vacuum assist cycle). This screenassists a user in selecting the most appropriate products for use in thehospital's sterilization monitoring or assurance systems. Optionally,additional information such as training, disposal procedures, set up orrecommendation information may be provided. For example, some test packsfor ethylene oxide sterilizers require an aeration period prior todisposal. The system according to the present invention may be designedto communicate proper disposal procedures to the user.

FIG. 25 is a view of the computer screen of a graphic user interface fora sterilization monitoring tracking system which identifies a particularpack to be subjected to a sterilization procedure 71, the contents ofthe pack 73, a load number, and steps to occur during a sterilizationmonitoring process 74, 75 and 76. The prompts 74, 75 and 76 can be usedto assist the user in properly performing sterilization assuranceprocedures adopted by a particular hospital. Prompts 74 and 76 can alsohelp correlate information from a sterilization indicator withinformation relating to the particular items to be sterilized (e.g. thepack contents 73). This information could be readily integrated into thehospital's inventory management database that typically includesinformation relating to standardized instrument sets, pack numbers,components of packs and set-up instructions. Placing this information inan information management system that includes a local area networkingfeatures (LAN) increases access to the information.

FIG. 25 is one example of how sterilization information may becorrelated with the actual articles subjected to a sterilizationprocess. In this figure, several articles within pack no. 9999 areidentified. For example, a user may manually enter the articles to besubjected to the sterilization cycle (the Metzenbaum clamp or trocarsshown in FIG. 25) into the computer database. Alternatively, the articleto be subjected to the sterilization cycle may optionally have a barcode associated with it, as described for example, in GermanOffenlegungsschrift No. DE 3 917 876 A1 or U.S. Pat. No. 5,610,811 (theentire contents of each of which are herein expressly incorporated byreference). That bar code could optionally be read and the informationautomatically identified to the computer database.

The load for the particular pack is also identified in FIG. 25. Packnumber 9999 is designed to be sterilized within a particular load(#410). If the items within pack 9999 should not be sterilized in thepredetermined load, the system may optionally provide a warning signalto the user. As an example, if the article to be sterilized cannotwithstand the heat of a steam cycle, the system of the present inventioncan send a warning to the user if load number 410 is to be a steamsterilizer load. As another example, if the sterilizer for a particularload (e.g. load number 410) is not approved for a particular type ofarticle to be sterilized (e.g. a surgical instrument with a lumen suchas a trocar), then appropriate information may be sent to the user.

It will be appreciated that there are many different safeguards thatcould be built into the system. As yet another example, if theparticular article to be sterilized needs to be cleaned prior to beingsubjected to the sterilization cycle, then the system can help ensurethat cleaning occurs prior to the article being sent to centralsterilization. Referring to FIG. 3, an article in decontamination 212can be identified as being cleaned or dirty. This information can bestored in the database of the system depicted in FIG. 4. If the statusof the article is “dirty”, then the system can provide a warning if auser attempts to distribute the item to central sterilization 202 priorto cleaning.

The proper set up and use of packs may be facilitated by thesterilization article tracking system according to the presentinvention. For example, the system according to the present inventionmay include illustrations of articles appropriate for the pack ormethods of optimally assembling particular items in the pack. This canhelp avoid packs that are loaded too densely or otherwise loaded in afashion that would interfere with the sterilization process.

In another aspect of the present invention, the screen shown in FIG. 25may be designed to prompt a user as to the proper series of steps totake according to the sterilization monitoring procedures adopted by thehospital. It should be noted that the system can be customized to adoptthe particular guidelines preferred by the hospital. Virtually any ofthe guidelines found in JCAH, AORN, ASHCSP, AORN and AAMI can be readilyincorporated in the system according to the present invention.

Referring again to FIG. 25, prompts 74 and 75 can link a chemicalindicator readout to articles within a sterilizer pack. Prompt 76 canlink a biological indicator readout to those same articles. Morespecific instructions relating to how to create a challenge pack mayalso be provided to the user.

The system according to the present invention may also be an element ofa recall system that helps prevent the use of products that are notsterile. FIG. 26 is an example of a computer screen that issues awarning and provides further instructions to a user. This may bepresented to a user if an attempt is made to send an article from afailed sterilization cycle to the operating room for use in a surgicalprocedure. It can also provide information to central sterilizationrelating to the performance of a particular sterilizer. Appropriateremedial measures may then be taken by the hospital.

Referring now to FIGS. 27 and 30, there are shown examples of samplecomputer screens for graphic user interfaces that may be utilized by ahospital to custom design its own chemical indicators. The computerscreen 391 allows a user to custom create his or her own chemicalindicator (e.g. for a particular pack) or obtain information relating tosterilization indicator selection for a particular sterilization cycle(e.g. a steam vacuum assist cycle).

FIG. 30 is an example of a screen that may appear if the user selects“create a bar code chemical indicator” (e.g. for a particular pack) inFIG. 27. Alternatively, the user can create his or her own indicatorindependent of the pack. This allows the hospital (as opposed to themanufacturer of the chemical indicator) to design the informationassociated with the chemical indicator.

The system depicted in FIGS. 27 and 30 may be readily integrated into ahealthcare facility's combined sterilization assurance and inventorysystem. The graphical user interfaces in FIGS. 27 and 30 are capable ofexchanging information between a user and computer means (e.g. personalcomputer 306 or mainframe 304 shown in FIG. 4).

FIG. 30 illustrates another example of how the system according to thepresent invention may associate sterilization information with aparticular article to be sterilized. As discussed above in relation toFIG. 25, the articles to be sterilized within a pack can be identifiedto a computer database. The chemical indicator created in FIG. 30 couldbe a label 410 for placement on a particular pack. The bar code shown inFIG. 30 could optionally be printed from a sterilization sensitive ink.As discussed above, a chemical indicator reader may be designed to readthe particular bar code and determine whether it indicates a adequate orinadequate sterilization cycle. Thus, the information relating towhether the sterilization cycle was adequate or inadequate can bedirectly linked to the articles subjected to the sterilization cycle.

Refering now to FIGS. 4 and 30, the computer (e.g. 304 or 306)preferably stores information relating to at least two types ofsterilization procedures (e.g. one of sterilization procedures 401, 402,403 or 404), at least two different types of sterilization sensitiveindicating inks corresponding to the sterilization procedures (e.g. inksfor creating a chemical integrator and inks for creating a processindicator), and at least one pattern for printing the inks (e.g. the barcode 405, a rectangular strip 406 or a custom designed shape for the ink407).

FIG. 14 illustrates an ink jet cartridge 100 for use with a printer 308that comprises an ink jet printer. The cartridge 100 has three differentink wells 102, 104 and 106 for different types of inks. For example, theink within well 102 could comprise a colorfast, permanent ink. The inkwithin well 104 could comprise an ink that is sensitive to a steamsterilization cycle while the ink within well 106 is sensitive to anethylene oxide sterilization process. The cartridge also includes anorifice 107 for dispensing the ink and a means for selecting ink fromthe wells 102, 104 and 106.

As shown in FIG. 30, the graphical user interface including means forselecting from information stored in the storage means of the computer.The system also includes printing means (e.g. printer 308, FIG. 4) forprinting the chemical indicator on a backing.

For example, the printing means may comprise an ink jet printer 308 withan ink jet cartridge having an ink jet printable, sterilizationsensitive indicating ink. Optionally, the system may include backingcorrelating means 408 for correlating a particular type of backing witha predetermined, compatible sterilization procedure. As depicted, thesoftware could include a feature that automatically selects anappropriate backing for a particular sterilization indicator.Alternatively, the software could simply include a “check substrate”dialogue box or merely a reminder to use a particular printer tray thathas been loaded with the appropriate substrate (e.g. tray 1 of theprinter is always paper while tray 2 is always polymeric). As anotheralternative, the printer could include a weight or density sensor toassist in identifying the appropriate backing material for theparticular sterilization indicator.

The system also preferably includes ink correlating means forcorrelating a predetermined sterilization sensitive indicating ink to asterilization procedure and for preventing the printing means fromprinting the predetermined ink. As an example shown in FIGS. 4 and 14,the printer 308 and ink jet cartridge 109 may include Hall sensors thatcan identify the particular type of cartridge 100 placed in the printer308 to the computer 306 or 304. If the ink jet cartridge 100 does notinclude an ink within well 102, 104, or 106 that is designed for usewith the particular sterilization cycle, the system can prompt the useto replace the cartridge with a cartridge having the appropriate ink.Once the hall sensor means indicates that the printer 308 is loaded withthe appropriate cartridge, the user may proceed to print out thesterilization indicator 410.

The advantage of the system shown in FIGS. 27 and 30 is that it createsthe chemical indicator at a location close to its actual use. On sitedata or needs help define the chemical indicator, not the manufacturer.As used herein, when it is said that a sterilization indicator isprinted at a healthcare facility, it means that the sterilizationindicator is actually completed at a hospital, surgical center, or otherfacility in which healthcare services are provided, as opposed to itbeing completed at a manufacturing facility that is substantiallydedicated to the manufacture of a sterilization indicator.

FIG. 30 illustrates some information 410 that can be included in thesterilization indicator. This information could be readily modifiedaccording to the healthcare facility's actual needs.

FIG. 28 is an example of a computer screen of a graphic user interfaceof a sterilization monitoring tracking system showing a particularitem's sterilization history. This screen is preferred for use in amethod of monitoring articles to be subjected to a sterilization processcomprising the steps of providing a sterilization indicator (e.g. achemical or biological indicator) capable of providing informationrelating to the efficacy of a sterilization process, an article to besubjected to the sterilization process (e.g. a trocar), a reading device(e.g. the bar code reader 312, the non-code reader 329, the autoreader327 and/or the through-the-pack monitor 328 (described in greater detailbelow) capable of obtaining information from the sterilizationindicator, and computer means (e.g. 306 and/or 304) for managinginformation associated with the sterilization indicator and the article;subjecting the sterilization indicator and the article to thesterilization process; reading information from the sterilizationindicator with the reading device; and associating information from thesterilization indicator with the article by use of the computer means.Unlike prior art systems, the sterilization history of a particularproduct is automatically recorded and managed and can be displayed, forexample, in the fashion shown in FIG. 28. The opportunity for humanerror is reduced.

It should be noted that the system shown in FIG. 4 is capable ofreceiving and processing diverse information. For example, with thethrough the pack monitor, the step of reading information from thesterilization indicator with said reading device includes the step ofreading the magnetic property or radio frequency signals of thesterilization indicator. With a chemical indicator scanning means of thepresent invention, the step of reading information from thesterilization indicator with said reading device may include the stepof: reading the infra red emissions from the sterilization indicator.With a biological indicator reader 327 the step of reading informationfrom the sterilization indicator with said reading device includes thestep of: reading fluorescence from the sterilization indicator.

Preferably, the computer means 304, 306 is capable of receiving,processing, transmitting, and printing data relating to the article andthe sterilization indicator.

FIG. 29 is a view of a computer screen of a sterilization monitoringtracking system showing steps associated with automatically reading achemical indicator. The prompts assist a user in properly operating amachine for automatically reading a chemical indicator. The first prompt521 can provide information to the controller (e.g. 81 of FIG. 17) ofthe scanning means. The information allows the controller to compare thereadout of the chemical indicator with data stored in nonvolatilememory. The next prompt 522 may be used to ensure that the positioningmeans of the scanning means is operating properly (e.g. the chemicalindicator is properly placed relative to the illumination and detectionelements of the scanning means). Finally, the scanning means can provideoutput 523 to the user.

In a preferred embodiment, the system is designed to assist a hospitalin complying with recommended practices, guidelines or other proceduresdesigned to meet a sterility assurance level. For example, the CDCGuidelines For Handwashing and Hospital Environmental Control (1985)specify that biological indicators should be used at least once a weekand in each load if it includes implantable objects. The system couldoptionally include a screen designed to remind the user that abiological indicator should be used with a particular load. As anotherexample, the AORN Recommended Practices for Sterilization in thePractice Setting (1997) sets forth that a biological indicator should beused when evaluating sterilization of new items. The system couldinclude a means for identifying new items, and a screen for remindingthe user that a biological indicator should be used in that particularload. Optionally, the system could include a means for disabling asterilizer or preventing its use in the event an operator deviates fromthe sterilization practices adopted by the hospital.

EXAMPLE 1

Eight gallons of white steam indicator ink were triple roller milledusing the composition described in Table 1a. The ink was screen printedon Monatec 5111-120 paper available from Monadnock Paper Mills,Bennington, Vt. The printed paper was cut to form indicator strips(Run 1) 20.3 centimeters long and 1.6 centimeters wide (8 inches by ⅝inch) and perforated in the middle. The strips were overcoated using a390 mesh screen with “UV #600” ultraviolet protector available fromMidwest Coatings, Inc., North Kansas City, Mo. The amount of inkdeposited after drying was 0.008 grams/square centimeter. Sheets werealso screen printed with white steam indicator ink on Type S-14526 paperavailable from Kimberly Clark, Atlanta, Ga. However the sheets were notovercoated (Run 2).

TABLE 1a White Steam Indicator Ink Formulation used in Runs 1-2Component Weight Generic Name Trade Name/Source/Address (percent) Leadcarbonate Halstab White Lead A/Halstab/ 24.88 Hammond, IN Sulfur#21-95/Akronchem/Akron, OH 08.56 Magnesium 5950/A R Mallinkrodt/St.Louis, MO 08.32 Carbonate Lithium Carbonate Cyclone Fine #400-A/Lithium02.68 Corporation of America/Gastonia, NC Binder ZephyrsetK-6544D/Sinclair and 55.56 Valentine/North Kansas City, MO

The Yellow Steam Indicator Strips (Run 3) were purchased from AlbertBrowne, Ltd., Leicester, U.K.

Green Steam Indicator Ink (Run 4) was made by grinding in a ball millthe composition described in Table 1b. The ink was screen printed onMonatec 5111-120 paper and dried.

TABLE 1b Green Steam Indicator Ink Formulation used in Run 4 ComponentWeight Generic Name Trade Name/Source/Address (percent) Copper CarbonateSigma-Aldrich Fine Chemicals/St. 32.1 Louis, Mo. Sulfur #21-95/AkronChemical Co./Akron, OH 08.1 Binder Zephyrset K-6544D/Sinclair and 59.8Valentine/North Kansas City, MO

Red Steam Indicator Ink (Run 5) was made by milling the compositiondescribed in Table 1c. The ink was printed using a Number 20 Meyer baronto Monatec 5111-120 paper and dried.

TABLE 1c Red Steam Indicator Ink used in Run 5 Component Weight GenericName Source, Address (percent) Nickel dimethylglyoxime 3M Company, St.Paul, MN 04.7 Disodium salt of ethylene E. M. Science, Gibbstown, NJ19.0 diamine tetraacetic acid Ethyl Cellulose Binder ColonialG-20-90-NL/Colonial 74.3 Printing Ink Co.,/East Rutherford, NJ AmmoniumThiocyanate Akzo Chemical of America, 02.0 Chicago, IL

Two Code 39 bar codes, A and B were prepared from a standard programusing a Zebra Stripe Bar Code Printer from Zebra Technologies Corp.,Vernon Hills, Ill. Code A is shown schematically in FIG. 1 and Code B isillustrated schematically in FIG. 2. Code A is *123456* and Code B is*12345 6* 7*. Code A can be scanned in either direction to give“123456”. Code B can be scanned in either direction to give 7. Acombination of Code A and Code B will read “1234567”. The ninth bar of*7* was cut out from Code B and scanned with an Intermer 9710 Bar CodeScanner from Intermec Corp., Everitt, Wash. The Code B bar code thenread “123456”. The strips and sheets which had previously been printedwith indicator inks described above for Runs 1-5, but unprocessed, werecut to replace the 9^(th) bar of *7* of Code B. This provided a ModifiedCode B which read “123456” when scanned. Modified Code Bs were processedfor six minutes at 132° C. in the 3013 Amsco Eagle steam sterilizer. InRun 1, the *7* had changed color from off-white to black. When scanned,the Modified and processed Code Bs read “1234567” (Run 1-4). Furtherresults are shown in Table 1d for inks described in Table 1a, Table 1b,the commercially available indicator strips described above, and Table1c. The number scanned is the number of Modified Code Bs scanned. TheNumber Read records the number of times the scanned Modified Code B'sread “1234567”.

TABLE 1d Scanning Results using Different Steam Indicator Inks and HuesNumber Read/ Steam Indicator Ink Hue Number Scanned Run Number BeforeAfter Before After Standard 20/20 Code B 1 White Dark Brown  0/30 28/302 Off White Black  0/30 30/30 3 Yellow Purple 30/30* 30/30 4 Green Black30/30 30/30 5 Red White  0/30  0/30 *One scanning resulted in a numberother than the Standard Code B.

The scanner detected the white to black color changes consistently.Additional indicator ink strips prepared as described for Run 1 wereprocessed at 132° C. in the 3013 Amsco Eagle steam sterilizer fordifferent time intervals to obtain degrees of color change. A Tan colorwas produced after ½ minute exposure, Brown after 1 minute, Dark Brownafter 2 minutes, 1/30 Modified Code Bs read “1234567” for the Tan stripsand 10/30 Modified Code Bs read “1234567” for the Brown strips and 28/30Modified Code Bs Read “1234567” for the Dark Brown strips. Coloredfilters could be used to detect other color changes which were not readby the scanner used in this example for Runs 3, 4, and 5.

EXAMPLE 2

An indicating composition for use in a hydrogen peroxide sterilizationprocedure was prepared by combining the elements of the formulationlisted in Table 2a.

TABLE 2a Component Weight Generic Name Name/Source/Address (percent)Acid Fuschin Sigma-Aldrich Fine Chemicals/St. 0.18 Sodium Salt Louis,Mo. Rhoplex I-545 Rohm & Haas Corp./Philadelphia, PA 36.30 ShellacBleached Mantrose Bradshaw Zinsser Group/ 18.20 Bone Dry Westport, CTEthyl Alcohol 18.20 Isopropyl Alcohol Exxon Chemical Corp./Houston, TX27.22

The ink formulation was gravure flood coated onto S&S 410 Grade FilterPaper from Schleicher & Schuell Corp., Keene, NH. Code 39 bar codes Bwere modified as described in Example 1. Ten Modified Code Bs weresterilized in a Sterrad 100 from Advanced Sterilization Products (ASP)full cycle and scanned as described in Example 1. The results are shownin Table 2b.

TABLE 2b Scanning Results Number Read/ Run Hue Number Scanned Number InkBefore After Before After Standard 20/20 Code B 1 Hydrogen Dark White 0/10 9/10 Peroxide Indicator Purple Ink

An incorrect scan angle can give false results.

EXAMPLE 3

U.S. Pat. Nos. 4,731,222; 4,892,706; 5,037,623; 5,077,008; and 5,091,343(the entire contents of each of which are herein incorporated byreference) describe liquid peracetic acid sterilization procedures forwhich the present invention may be employed.

Indicator strips available from Steris Corp., Mentor, Ohio were used tomonitor a sterilization process including the use of a liquid peracidicacid solution (e.g. the STERIS SYSTEM 1™ AND Steris 20™ SterilantConcentrate available from Steris Corp.). The ninth bar of Code B wasreplaced with strips cut from the indicator strips before and aftersterilization in the Steris System 1™ Full Processing Cycle. TheModified Code Bs were scanned as described in Example 1. The results areshown in Table 3a.

TABLE 3a Scanning Results Number Read/ Run Hue Number Scanned Number InkBefore After Before After Standard 20/20 Code B 1 Commercial Dark PaleBlue  0/10 9/10 Indicator Strips Purple (Steris)

An incorrect scan angle can give false results.

EXAMPLE 4

“3M™ Comply™ ‘00311’ Dry Heat Indicator Strips” from 3M, St. Paul, Minn.were used to monitor a dry heat process. The ninth bar of Code B wasreplaced with strips cut from the indicator strips before and afterheating in a Tenney Jr. oven for 1 hour at 160° C. The Modified Code Bswere scanned as described in Example 1. The results are shown in Table4b.

TABLE 4b Scanning Results Number Read/ Run Hue Number Scanned Number InkBefore After Before After Standard 20/20 Code B 1 3M ™ Comply ™ TanBlack  2/10 10/10 ‘00311’ Dry Heat Indicator Strips

EXAMPLE 5

“3M™ Comply™ ‘00152’ Ethylene Oxide Sterilometer Strips” from 3M, St.Paul, Minn. were used to monitor an ethylene oxide sterilizationprocess. The ninth bar of Code B was replaced with strips cut from theindicator strips before and after processing in a 3M 4XL Ethylene OxideSterilizer on a full warm cycle. The Modified Code Bs were scanned asdescribed in Example 1. The results are shown in Table 5a.

TABLE 5a Scanning Results Number Read/ Run Hue Number Scanned Number InkBefore After Before After Standard 20/20 Code B 1 3M ™ Comply ™ LightBlue  0/10 8/10 ‘00152’ EO yellow Sterilometer Strips

Colored filters could be used to detect this color change which wasdifficult to read using this bar code scanner.

EXAMPLE 6

Tests were conducted to determine whether a reading device couldaccurately read existing, publicly available chemical indicators.Thirty-seven (37) spectral scans were conducted on twenty-two (22)different sterilization indicator strips.

Four different types of sterilization indicator strips were exposed tovarious levels of sterilants or partial cycles. As shown in FIG. 15, adevice was configured on a Newport optical bench from off the shelfinstrumentation to spectrally scan the indicator strips. Scanning wasdone in a photographic quality darkroom to suppress ambient light. Theillumination source was Flexilux 250 (endo available from SchollyFiberoptic GMBH of Denzlingen, West Germany) using an Osram 418 flquartz halogen lamp (3200 degree K). No filter was used and the opticalaperture was fully open. Power was provided to the lamp from 118.9 VoltsAlternating Current (VAC) Root Mean Square (RMS) 60 Hertz (HZ). A fiberoptic light guide was used to transfer visible light to the indicatorstrip while blocking infrared (heat). The fiber consisted of a packedsmaller glass fiber circular array with 4.78 mm core diameter. Nofocusing optics were used with the illumination fiber. The illuminationsource was powered up and allowed to equilibrate for 10 minutes beforescanning. Dark field scans were taken before and after scanning theindicator strips to confirm illumination source stability.

The detector was an Ocean Optics S2000 fiber optic spectrometeravailable from Ocean Optics of Dunedin, Fla. Two quartz fibers(P600-2-SMA) (2 meter in length by 600 micrometers in diameter), afilter holder (FHS-UV), and a collimating lens (74-UV) were used tocollect light from the indicator strip. The effective aperture at theplane of the indicator strip was approximately 3 mm in diameter. Thespectrometer was connected to a personal computer running the OOI baseV1.5 application available from Ocean Optics of Dunedin, Fla. Data wasfurther parsed and charts were generated in Microsoft EXCEL.

Newport positioning devices were used to hold the detection fiber andillumination fiber in fixed geometric relation to the plane of theindicator strip. Illumination incident angle was set at 45 or 90 (FIG.16) degrees from the plane of the indicator strip. Detector fiber andillumination fibers were 2.5 inches above the plane of the indicatorstrip. A flat black paper was placed on the optical bench to restrictstray reflections.

The first set of indicator strips tested was prepared as described inExample 1 for the white steam indicator ink and overcoated with anultraviolet coating. This chemical indicator is designed to monitor anysteam sterilization cycle. It changes from white to dark brown/blackafter six minutes exposure at 132° C. in the 3013 Amsco Eagle steamsterilizer. FIG. 6 shows three spectral scans made at a 90 degreeillumination incidence angle for three white steam indicator strips.After the first steam indicator strip was exposed for six minutes at132° C. in the 3013 Amsco Eagle steam sterilizer, it appeared black 502(exposed to sterilant). After a second steam indicator strip was exposedfor two minutes at 132° C. in the 3013 Amsco Eagle steam sterilizer, itappeared brown 504 (partial exposure). A third indicator strip was notexposed to any portion of a sterilization cycle and it appeared white500 (no exposure). These indicator strips had specular first surfacesdue to the ultraviolet overcoat.

FIG. 7 shows the scans of the same indicator strips that were used forFIG. 6 but the scans were made at a 45 degree illumination incidenceangle. Reference character 510 represents black (exposed to sterilant),character 508 brown (partial exposure), and character 506 white (noexposure). Note the improved differences in relative intensity for thecontrast changes.

The second set of indicator strips was “3M™ Comply™ ‘00152’ EO ChemicalIndicator Strip”. This indicator strip is designed to monitor theethylene oxide (EO) sterilization process. It changes from yellow toblue when exposed in a 3MTM SteriVac™ 4XL Ethylene Oxide Sterilizer on afull warm cycle.

FIG. 8 shows spectral scans made at a 90 degree illumination incidenceangle for five EO chemical indicator strips. After two EO indicatorstrips were exposed for a full warm EO cycle, they appeared blue 512,520 (fully exposed to sterilant). After a third EO indicator strip wasexposed for 10 minutes, it appeared yellow/green 514 (partial exposure).After a fourth EO indicator strip was exposed for 30 minutes, itappeared green 518 (more exposure). A fifth EO indicator strip was notexposed to any portion of a sterilization cycle and it appeared yellow516 (no exposure). These indicator strips also had specular firstsurfaces due to a plastic lamination to prevent the surface of the inkfrom coming in contact with items being sterilized. Note the variabilityfor reading of the two blue indicator strips 512, 520 in FIG. 8 whichwere fully exposed to sterilant; and therefore, should be similar toeach other if not the same.

FIG. 9 shows scans of the same indicator strips made at a 45 degreeillumination incidence angle. They appeared blue 528 (exposed tosterilant), yellow/green 524 (partial exposure), green 526 (lessexposure), yellow 522 (no exposure). Note the improved spectraldiscrimination.

The third set of indicator strips was “3M™ Comply™ EO Chemical IndicatorStrip”, Model 1251. This indicator strip is designed to monitor theethylene oxide (EO) sterilization process. It changes from red to greenwhen exposed in a 3M™ SteriVac™ 4XL Ethylene Oxide Sterilizer on a fullwarm cycle.

FIG. 10 shows spectral scans made at a 90 degree illumination incidenceangle for four model 1251 EO indicator strips. After a first EOindicator strip was exposed for 60 minutes at 50% relative humidity(RH), it appeared green 530 (exposed to sterilant). After a second EOindicator strip was exposed for 30 minutes at 90% RH, it appeared olive534 (partial exposure). After a third EO indicator strip was exposed for21 minutes at 30% RH, it appeared brown 536 (less exposure). A fourth EOindicator strip was not exposed to any portion of a sterilization cycleand it appeared red 532 (no exposure). These indicator strips hadspecular first surfaces made by covering the exposed ink with clear“Scotchm Mailing Tape”.

FIG. 11 shows scans of the same EO indicator strips of FIG. 10 but madeat a 45 degree illumination incidence angle. They appeared green 538(exposed to sterilant), olive 540 (partial exposure), brown 546 (lessexposure), and red 542 (little exposure). Note the improved spectraldiscrimination. The olive and red indicator strips have curves that arevery similar in shape as well as intensity when scanned using a 90degree illumination incidence angle (FIG. 10). In contrast, the curvesfor the same two indicator strips have quite apparent differences whenscanned using a 45 degree illumination incidence angle especially atwavelengths of between 500 and 550 nanometers (FIG. 11).

The fourth set of indicator strips were the same as the indicator stripsused for FIG. 10 and FIG. 11 except the ink was not covered or coated.The first surfaces are diffuse not specular.

FIG. 12 shows spectral scans made at a 90 degree illumination incidenceangle for four Model 1251 EO indictor strips. After a first EO indicatorstrip was exposed for 60 minutes at 50% relative humidity (RH), itappeared green 548 (exposed to sterilant). After a second EO indicatorstrip was exposed for 30 minutes at 90% RH, it appeared olive 550(partial exposure). After a third EO indicator strip was exposed for 21minutes at 30% RH, it appeared brown 552 (less exposure). A fourth EOindicator strip was not exposed to any portion of a sterilization cycleand it appeared red 554 (no exposure).

FIG. 13 shows scans of the same EO indicator strips of FIG. 12, but madeat a 45 degree illumination incidence angle. They appeared green 556(exposed to sterilant), olive 558 (partial exposure), brown 562 (lessexposure), and red 560 (no exposure). Note the improved spectraldiscrimination.

This example shows that specular first surface indicator strips measuredat a 90 degree illumination incidence angle were sensitive to flatnessand geometric position. Preferable geometry for a reader of theseexisting sterilization indicators would include detection normal to theplane of the indicator strip and illumination at a 45 degree incidenceangle to the plane of the indicator strip.

Readers

Referring now to FIGS. 7 and 19 and example 6, there is shown a methodof determining whether the sterilization indicator has been subjected toan adequate sterilization process. Curves for the various sterilizationcycles are shown in FIG. 7. Curve 510 was generated from a sterilizationindicator that was subjected to an adequate sterilization process.Curves 506 and 508 were generated from sterilization indicators thatwere subjected to inadequate sterilization processes.

A suitable range of wavelengths may be selected. For example, in FIG.19, the range is between 493 and 635. A maximum intensity may then beselected by, for example, obtaining intensity information fromsterilization indicators subjected to a sterilization cycle known to beadequate. In this example, the intensity selected is 500.

The reader can then read the sterilization indicator, compare the readintensity with the selected maximum and determine whether it exceeds themaximum. The determination of whether the sterilization cycle wasadequate (fully processed or not fully processed) may then be made asshown in FIG. 19.

EXAMPLE 7

This example demonstrates a method and formulation for placing achemical indicator ink into a desk jet printing cartridge. Ink jetprinting technology is described in U.S. Pat. Nos. 4,872,026; 4,907,018;5,594,483 and 5,874,978 (the entire contents of which are hereinincorporated by reference). An ink jet printed sterilization indicatorallows the user to print her/his own name, identification, or patternonto the label of something being processed in a specific chemicalenvironment. By placing several inks into these cartridges, one createsa manufacturing process whereby different inks can alternately be placedon a web, depending on the production demand. This would allow one(preferably an automated) assembly line, with many outputs, to replaceseveral existing lines. FIG. 14 is a perspective view of arepresentative ink jet printer cartridge 100 designed to hold threedifferent indicator ink chemistries in compartments 102, 104, and 106.The compartments are covered so that the inks cannot leak or mix betweencompartments.

A vapor hydrogen peroxide/plasma chemical indicator was prepared byusing the composition shown in Table 7a and Table 7b.

TABLE 7a Sterrad Indicator Ink Composition Component Weight Generic NameTrade Name/Source/Address (grams) Acid Fuchsin Sodium Salt Sigma-AldrichFine Chemicals, 2.5 St. Louis, MO Deionized water 50 Polyethylene glycol200 Exxon Chemical Company, 20 Houston, TX

TABLE 7b Sterrad Indicator Ink Composition Component Weight Generic NameTrade Name/Source/Address (grams) Acid Fuchsin Sodium Salt Sigma-AldrichFine Chemicals 2.5 Water soluble green dye DB-892 Colorcon, West Point,PA 0.6 Deionized water 50 Ethylene glycol Sigma-Aldrich Fine Chemicals10 Diethylene glycol Sigma-Aldrich Fine Chemicals 10

The composition was prepared by mixing the components of the compositiontogether in a 16 ounce bottle on a paint mixer until the solid particleswere dissolved. The composition was then filtered through Whatman # 4filter paper from Whatman, Inc., Clifton, N.J. to remove the particlesizes greater than 20-25 micrometers which might clog an ink jetcartridge. Next the compositions were placed in an ink jet cartridge fora Hewlett Packard (HP) desktop printer and were printed on a 216 by 279mm, white, 75 grams per square meter, sheet of Cascade™ X-9000 copypaper from Boise Cascade Paper Division, Boise ID using PowerPointsoftware from Microsoft, Redmond, Wash. These were then “laminated”front and back with Scotch™ Magic™ tape.

The composition described in Table 7a was also printed on polyester filmwith a polyvinylidene chloride (PVDC) coating available as 3MTransparency Film CG3460 from 3M Company, St. Paul, Minn. Referring toFIG. 5, indicator ink 254 was printed on polyester film 256 usingPowerPoint. The indicator ink was covered with a lamination of anadhesive layer 252 and a film layer 250. The adhesive layer 252 wasprepared using an isooctyl acrylate/acrylamide adhesive binder and anisooctyl acrylate/acrylic acid (IOA/AA) copolymer microsphere system asdescribed in PCT publication no. 94/194420 or its priority document U.S.patent application No. 08/018,927, filed Feb. 16, 1993, 3M attorneyReference No. 49441USA3A, entitled, “System Comprising Release Agent andHigh Peel Adhesion Repositionable Adhesive” by L. Bilski, R. Kumar, T.Mertens, and S. Wilson (the entire contents of which are hereinincorporated by reference). The film layer 250 was a 2.5 mil polyesterfilm that is transparent and has good heat stability coated with aprimer to aid in bonding of the adhesive to the backing.

When exposed to a standard Sterrad 100 Hospital cycle (44 minutes ofhydrogen peroxide diffusion) and when exposed for shorter period oftimes such as 23 and 36 minutes, the above constructions demonstratedtheir ability to perform as moving front indicators. The hydrogenperoxide diffuses either through the paper as in the case of theindicator ink printed paper sandwiched between two films or through themicrosphere/ binder adhesive 252 as in the case of the indicator inkcovered by IOA/AA microspheres and adhesive binder. The moving frontprogresses toward the center of the device as it is exposed for longerperiods of time. The paper substrate used could be varied (othercellulosics, perhaps nonwovens) depending on the environment of exposureor the production demands. The adhesive used could be any microsphereadhesive which would allow the diffusion of hydrogen peroxide such asthose described in U.S. Pat. Nos. 3,691,140; 4,166,152, 4,049,483;4,855,170 and 3,857,731. If neither the backing 256 for the indicatorink chemistry or the adhesive layer 252 are permeable to the sterilant,then the indicator ink chemistry should be exposed directly to thesterilant.

Another advantage of using the ink jet cartridge is that the ink isprinted in very small dots of color (600 dpi in this example). This aidsthe observer's ability to see the location of the front since themovement of the peroxide either reacts with a given dot or not leaving aclearly defined line between the green (reacted) and purple (unreacted)hues.

On the individual user basis, the ink jet cartridge allows a user toprint their own indicator patterns and identification. It also providesmore labeling options (ID trays, etc. on labels). For example, theinformation provided on the label 410 in FIG. 30 could be modifiedaccording to the desires of the users, not the manufacturers.

Several different types of sterilization indicator processes could beused. A large variety of inks, timings, substrates, etc. could be placedon one large assembly line. This would allow greater versatility, lowercost, fewer operators, and greater precision in the plant.

READERS EXAMPLE 7

The chemical indicator described in Table 7a visually changes frompurple to green when exposed to a vapor hydrogen peroxide plasma phasefor a certain amount of time and at a certain concentration of hydrogenperoxide. Along with this visual change, a corresponding change in thewavelength at which the indicator absorbs light can also be detected. Achromaticity diagram shows that this corresponds to an initial primaryabsorbance at approximately γ₀=460 nm (unexposed) and a final absorbanceat approximately γ₁=495 nm (fully exposed).

The processor of a reader or scanner for this chemical indicator may beprogrammed such that the initial (unexposed) indicator's primaryabsorbtion relative intensity is set to 100%. As the individualmolecules of the indicator chemistry react, they will begin to absorb ata different wavelength (γ₁). As the sterilization cycle proceeds, therewill be a decrease in the relative intensity (from RI_(0, init) toRI_(0, final)) of γ₀ and an increase in relative intensity (fromRI_(1,init) to RI_(1, final)) of γ₁.

Alternatively, other algorithms could be utilized to enable the readerto automatically evaluate the indicator and determine if adequatesterilization conditions occurred.

In a first embodiment, the processor may be programmed to respond to theremaining relative intensity of γ₀. This threshold value (a) (seeequation below) should correspond to a suitable decrease in the initialcolor to represent an “accept” cycle of the sterilizer. That is:${{{IF}\quad ( \frac{{RI}_{0,{initial}} - {RI}_{0,{final}}}{{RI}_{0,{initial}}} )} \leq a},$

THEN “ACCEPT” or “ADEQUATE”${{{IF}\quad ( \frac{{RI}_{0,{initial}} - {RI}_{0,{final}}}{{RI}_{0\quad {initial}}} )} > a},$

THEN “REJECT” or “INADEQUATE”

In a second embodiment, the processor may be programmed to respond tothe increase of relative intensity of γ₁. The threshold value (b) (seeequation below) should correspond to a suitable increase in the finalcolor to represent an “accept” cycle of the sterilizer. That is:${{{IF}\quad ( \frac{{RI}_{1{finall}} - {RI}_{1,{initial}}}{{RI}_{1{finall}}} )} \leq b},{{{IF}\quad ( \frac{{RI}_{1{finall}} - {RI}_{1,{initial}}}{{RI}_{1{finall}}} )} > b},$

THEN “ACCEPT” or “ADEQUATE”

THEN “REJECT” or “INADEQUATE”

In yet another embodiment, a combination of the two factors can beimplemented:$( {{{IF}\quad ( \frac{{RI}_{0,{initial}} - {RI}_{0,{final}}}{{RI}_{0,{initial}}} )} \leq a} )$

AND$( {{{IF}\quad ( \frac{{RI}_{1{finall}} - {RI}_{1,{initial}}}{{RI}_{1{finall}}} )} \leq b} ),$

THEN “ACCEPT” or “ADEQUATE”$( {{{IF}\quad ( \frac{{RI}_{0,{initial}} - {RI}_{0,{final}}}{{RI}_{0\quad {initial}}} )} > a} )$

OR$( {{{IF}\quad ( \frac{{RI}_{1{finall}} - {RI}_{1,{initial}}}{{RI}_{1{finall}}} )} > b} ),$

THEN “REJECT” or “INADEQUATE”

Yet another embodiment includes the step of integrating the relativeintensities over a range of wavelengths surrounding the initial andfinal colors instead of using two discrete wavelength values. Othermathematical correlations of these parameters could be used to maximizesensitivity and increase the safety margin.

The threshold values (a) and (b) can be arrived at by using informationtaken from reference indicators subjected to a sterilization cycle knownto be adequate or marginally adequate.

By implementing an algorithm that is based on the percentage of adiscrete or range of wavelengths, it is possible to include the optionof a self-calibrating reader. This is made possible both by means of theearlier algorithms, which use relative changes instead of absolutechanges in relative intensities, and by means of appropriate logicprogramming and memory. The self-calibrating reader would initially readthe indicator absorbance over the band of the visible spectrum. By logiccircuitry, the reader would establish its own baseline and determine thewavelength, or range thereof, that has the greatest absorbance. From agroup of spectra stored in its reference memory, it could be programmedto determine which type of sterilization indicator it was viewing (e.g.a steam chemical indicator, an ethylene oxide chemical indicator ormodels thereof). For instance, if the reader found that the maximumabsorbance of the chemical indicator was in the range of 760 nm, thereader itself would be able to determine that this represents a certainpurple indicator that is sensitive to hydrogen peroxide. The reader canalso read from memory that this indicator should finally achieve aspectrum that shows an absorbance at 495 nm—along with a value ofrelative change of both relative intensities.

If a color standard were also employed, the reader could determine itsown life cycle. That is, as it notes that a relative intensity for thestandard has shifted (due to bulb fatigue, scratches on optics, weakbattery, etc.), it can make the corresponding shifts in its logic tocompensate for the changes. If the memory contained spectra of multiplestages of each sterilization cycle, it would also be able to establishwhich parameters have not been met. Additionally, it may also be able toquantify how far from adequate the parameters are as well.

The present invention has now been described with reference to severalembodiments and examples thereof. It will be apparent to those skilledin the art that many changes or additions can be made in the embodimentsdescribed without departing from the scope of the present invention.Thus, the scope of the present invention should not be limited to thestructures described in this application, but only by structuresdescribed by the language of the claims and the equivalents of thosestructures.

What is claimed is:
 1. A method of monitoring the efficacy of asterilization process comprising the steps of: subjecting a chemicalindicator to a sterilization process, the chemical indicator comprising:i) a substrate having a surface, and ii) sterilizing agent sensitiveindicia associated with said surface of said substrate, said indiciahaving: (a) a first state prior to being exposed to the sterilizationprocess, and (b) a second state after being exposed to saidsterilization process, wherein the first state is different than saidsecond state, and at least said second state is machine readable; andscanning the indicia of the chemical indicator with a machine to obtaininformation relating to the sterilization process.
 2. A method accordingto claim 1 wherein the indicia comprises a code and the step of scanningthe indicia of the chemical indicator includes the step of reading theindicia of the chemical indicator with a code reader.
 3. A methodaccording to claim 2 wherein the indicia comprises a bar code and thestep of scanning the indicia of the chemical indicator includes the stepof reading the indicia with a bar code reader.
 4. A method according toclaim 1 wherein the first state is a first color and the second state isa second color, and the step of scanning the indicia of the chemicalindicator includes the step of distinguishing said first color from saidsecond color.
 5. A method according to claim 4 wherein the step ofdistinguishing said first color from said second color comprises thesteps of: a) providing reference information, b) reading informationfrom said chemical indicator, and c) comparing the information read fromsaid chemical indicator with said reference information.
 6. A methodaccording to claim 1 wherein the step of subjecting a chemical indicatorto a sterilization process comprises the step of subjecting a chemicalindicator to a steam sterilization process.
 7. A method according toclaim 1 wherein the step of subjecting a chemical indicator to asterilization process comprises the step of subjecting a chemicalindicator to an ethylene oxide sterilization process.
 8. A methodaccording to claim 1 wherein the step of subjecting a chemical indicatorto a sterilization process comprises the step of subjecting a chemicalindicator to a hydrogen peroxide sterilization process.
 9. A methodaccording to claim 1 wherein one of the first and said secondindications is not readable, and said step of scanning the indiciaincludes the step of reading only one of said first and said secondindications.
 10. A method according to claim 1 wherein at least one ofsaid first and second indications is readable and said step of scanningthe indicia includes the step of reading said first and said secondindications.
 11. A method according to claim 1 wherein step of scanningthe indicia includes the step of determining whether the chemicalindicator has reacted to all critical parameters of a predeterminedsterilization process.
 12. A method according to claim 1 wherein step ofscanning the indicia includes the step of determining whether thechemical indicator has reacted to time, temperature and saturated steam.13. A method according to claim 1 further including the step ofdetermining whether the sterilization process was an adequatesterilization process.
 14. A method of monitoring the efficacy of asterilization process comprising the steps of: a) providing a chemicalindicator comprising indication means having a first indicating stateprior to being exposed to the sterilization process and a secondindicating state after exposure to at least a portion of thesterilization process, such that the first indicating state is differentthan said second indicating state, and at least one of said first andsaid second states is machine readable; b) subjecting the chemicalindicator to the sterilization process, c) scanning the chemicalindicator with a machine to determine whether the sterilization processwas adequate.